Roman Science Pitch

An overview of the content of the science pitch submissions can be found in this STScI Newsletter article.

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Name Affiliation Co-authors Title Pitch Survey Category Keywords
Allison Youngblood NASA Goddard Space Flight Center Stellar Flares in the Roman Galactic Bulge Survey The Roman Space Telescope's Wide Field Instrument (WFI) and the planned Core Community Surveys are expected to provide ancillary science that reach far beyond the primary mission objectives. As was discovered with other wide field imagers, the stable photometry necessary for exoplanet discovery is well-suited to general stellar astrophysics, including flares, oscillations, and rotational modulation. While stellar astrophysics is not a primary science objective for Roman, it may eventually dominate Roman's total science output as measured by publications, as has happened for Kepler and TESS. Of particular note are stellar flares, which are important for understanding stellar magnetic activity and even the space weather environments of exoplanets.

Large stellar flare surveys have never been performed before in the Roman spectral range, and Roman may reveal new information about flare emission mechanisms (blackbody, recombination continuum, chromospheric emission lines) and how flare rates change with stellar age and metallicity. For example, the Galactic Bulge stars will be much older than the typical flare stars studied, and Roman's wide field and exquisite imaging may provide sufficient statistics to probe flare behavior and properties of such an old stellar population. However, the yield of information will likely depend on sky location, filters, cadence, and even read out strategy. Stellar flare timescales range from seconds to hours, so Roman may only be sensitive to the longest, most energetic flares.
Galactic Bulge Time Domain Survey stellar physics and stellar types n/a
Arash Bahramian Curtin Institute of Radio Astronomy Demystifying hidden black holes and neutron stars in the Galactic Bulge X-ray binaries (XRBs) are binary systems containing black holes or neutron stars accreting from a companion star. Many aspects of these systems remain poorly understood. These include their formation, distribution and behavior. Formation of XRBs (particularly XRBs with low-mass companions) is challenging to explain, as the supernova that forms the compact object in these systems is expected to disrupt the binary through natal kick. Their distribution is poorly understood as there is a large gap between the observed number of XRBs (~a few hundred) and theoretically predicted numbers (thousands). Lastly, their behavior is poorly understood - particularly in early rise of an "outburst" (enhanced accretion episode) as this phase can be radiatively inefficient and faint in the X-rays, thus generally missed by all-sky X-ray monitors. Outbursts in these systems are generally only detected when enhanced X-ray emission is noticed, which is typically days if not weeks after the actual start of the outburst. This makes the initial phase of an outburst rarely observed, making identification of the dominant processes igniting these outbursts challenging.

The Galactic Bulge harbors a large population of XRBs and candidates. Specifically, the area planned for the Roman Galactic Bulge Time Domain Survey overlaps significantly with a section of the bulge surveyed by the Chandra Galactic Bulge Survey (Jonker et al. 2011, ApJS, 194, 18) and the Swift Galactic Bulge Survey (Bahramian et al. 2021, MNRAS, 501, 2790), revealing more than a hundred X-ray sources within this region of overlap. The planned Roman Galactic Bulge Time Domain Survey enables us to make significant advances on all the poorly understood aspects mentioned above. First, the overlap of UV and X-rays in this region allows us to identify faintly accreting XRBs among unclassified X-ray sources and thus enables us to take a key step towards understanding the Galactic distribution of XRBs through identification of hidden XRBs in the Galactic bulge. Second, the astrometric precision of the Roman observatory combined with the enhanced UV emission expected from XRBs (due to accretion, compared to the optical emission which is dominated by emission from the companion) enables a detailed study of the kinematics of XRBs in this region through characterisation of their parallax and proper motion, which hold signatures of the system's supernova natal kick (e.g., Atri et al. 2019, MNRAS, 489, 3116). This will enable us to explore the link between XRB formation and supernova kick thoroughly, particularly in a swath of XRBs that have been too faint for VLBA astrometry (due to low accretion) or Gaia astrometry (small/stripped companion). Lastly, the high cadence monitoring provides the chance to catch and finely monitor an XRB outburst extremely early in the UV before X-ray enhancement, for the first time with such a level of coverage. The lag between the observed enhancement in the UV and X-rays is directly linked to the viscosity of the accretion disk, thus allowing us to characterize the ignition process in outbursts in detail. The nominal region chosen by the Roman Galactic Bulge Time Domain Survey and its overlap with high resolution high energy surveys (such as the Chandra bulge survey) is of paramount importance to enable exploration of Galactic Bulge XRBs deeply in the UV for the first time.
Galactic Bulge Time Domain Survey stellar physics and stellar types Astrometry, Binary stars / Trinary stars, Neutron stars, Stellar accretion disks
Bob Ellis independent Genosys The search for life is targeting pecusor for RNA. Chech has show that RNA is self replicating without the need for DNA "prof. Check" .

Using the NIR spectrometer scanning in stars and nebula the footprint for RNA and its precursors could give clues to biotic synthesis in space
Galactic Bulge Time Domain Survey solar system astronomy, exoplanets and exoplanet formation, stellar populations and the interstellar medium, galaxies, the intergalactic medium and the circumgalactic medium RNA, nucleotides, ribose , deoxyribose
Casey Lam UC Berkeley Jessica Lu (UC Berkeley), Sean Terry (UC Berkeley), Natasha Abrams (UC Berkeley) Finding isolated black holes with the Galactic Bulge Time Domain Survey Although there are estimated to be of order 100 million isolated black holes (BHs) in the Milky Way, only a single one has been characterized. This results in significant uncertainties about the properties of Galactic BHs, such as their mass distribution, velocities, and binary fraction. These BH properties are needed to constrain the highly uncertain physics of massive stellar evolution, such as implosion/explosion mechanisms and the types and importances of different binary interactions, which in turn impact chemical enrichment, gravitational wave sources, and galaxy formation and evolution.

Roman's Galactic Bulge Time Domain Survey (GBTDS) is the best opportunity to find and characterize hundreds of isolated Galactic BHs via microlensing. The survey requirements needed to find cold exoplanets are highly complementary to those needed to find BHs. The main difference is the timescale of the events of interest. Planetary signals tend to be short, requiring extremely high (<15 min) cadence to characterize, while long overall temporal coverage (>60 days) is not crucial. BH signals tend to be long, and while they do not require such a high cadence (~10 days for detection, ~1 day for characterization), long temporal coverage is much more important. Thus, for any Bulge observing windows during which the GBTDS is not planning to observe at high cadence, observations once a day or so toward the GBTDS fields will significantly increase the science return of the mission at minimal extra observation time. In addition, to fill in gaps when the Bulge cannot be observed with Roman, complementary observations from the ground will be crucial to better characterize these long events (such as wide-field photometry with the PRIME telescope, a collaboration between NASA and JAXA designed to observe synergistically with Roman; or targeted astrometry from the Keck telescopes). Any extensions to Roman's prime 5-year mission will also enable more candidates to be characterized, and will be extremely beneficial to obtaining the long astrometric baselines needed to measure BH masses.
Galactic Bulge Time Domain Survey stellar physics and stellar types, stellar populations and the interstellar medium n/a
Daisuke Kawata MSSL, UCL, UK Naoteru Gouda (NAOJ), Takafumi Kamizuka (The University of Tokyo), Hajime Kawahara (ISAS/JAXA), Naoki Koshimoto (NASA Goddard/UMD), Shota Miyazaki (ISAS/JAXA), Shogo Nishiyama (Miyagi University of Education), Ryou Ohsawa (NAOJ), Daisuke Suzuki (Osaka), Masahiro Takada (Kavli IPMU/Tokyo) Roman+JASMINE Galactic Center Astrometry Survey The Galactic center region (Rgc<~100 pc), including the Nuclear Star Cluster and Nuclear Stellar Disk, is the heart of our Galaxy and the place holding the historical treasures accumulated since the beginning of the formation of the Galaxy. It is also the highest density region of the Galaxy, harbouring the super massive black hole (SMBH). In the last decades, multi-wavelength observations have revealed fascinating phenomena, such as the motion of the stars around SMBH, the Fermi bubble, various high-energy sources, intermediate mass BH candidates and the complex structure of the central molecular zone. However, because of the severe dust extinction and the large and dense stellar structure, the measurements of stellar kinematics in the Galactic center are still limited, due to the small field of view (FoV) of high-resolution space or adaptive optics (AO) near-infrared (NIR) facilities and the limited spatial resolution of the large FoV facilities. With its unique survey capability with wide-field, high-resolution and high-sensitivity, the Nancy Grace Roman Space Telescope is the ideal facility to explore the Galactic center stellar structure and also 5 years of operation enables the measurements of the proper motion of the stars, i.e. astrometry. The precise astrometry will open up the new sciences, such as detecting long-time-scale (>100 days) astrometric microlensing event due to the black holes (e.g. Toki & Takada arXiv:2103.13015; Sajadian & Sahu arXiv:1301.03812), measuring the age distribution of the kinematically selected nuclear stellar disk, which will tell us the formation epoch of the Galactic bar (e.g. Baba & Kawata 2020, MNRAS, 492, 4500) and testing the existence of the Ultra Light Dark Matter (10^-22 - 10^-18 eV) core (e.g. Toguz et al. 2022, MNRAS, 511, 1757).

Hence, we propose to observe the Galactic center field of |l|<0.5 deg and |b|<0.4 deg (~5 pointings) with three filters at least twice per year when the Galactic center is observable. This field overlaps with the Galactic Center Survey field of the Japanese NIR astrometry mission, JASMINE, planned launch in 2028 by ISAS/JAXA. Taking an advantages of the similar operation period of Roman to JASMINE, we propose to observe this field with 5 sets of dithering observations (~20 images per filter to sample PSF) with 3 different filters, taking the shallow images with F087 (not saturate for 15 mag stars, but also deep enough to ensure the astrometric accuracy of faint stars) and the deep images with F158 (<~21 mag) and F213 (<~21 mag). Note that the final choices of the size of the field, filters and the depth are subject to further studies. The shallow images with F087 can avoid the saturation of the astrometric reference bright stars whose astrometry is accurately measured by JASMINE (J<12.5 mag) and Gaia (G<16 mag), which will be used to calibrate astrometry of the fainter stars (F087~20 mag). The calibrated astrometry for the fainter stars in F087 images will be used for the reference stars for the deeper images with F158 and F213. We aim to reach the well calibrated proper motion of ~0.03 mas/yr (~1.2 km/s velocity uncertainty at the distance to the Galactic center) for a few million stars of <21 mag stars in F158 (c.f. WFIRST Astrometry Working Group 2018, JATIS, 5, 044005; Hosek et al. 2022, ApJ, 939, 68). F213 images will be used to measure the colour of the faint stars and also detect the fainter sources, including the microlensing event. The proposed field will be also observed by Subaru's next generation AO instrument, ULTIMATE-SUBARU. Hence, the legacy value of the Roman+JASMINE Galactic Center Survey will be extremely high. Combination with ULTIMATE-SUBARU observations of additional few years will increase the potential to find long time-scale phenomena, such as the astrometric microlensing by the intermediate mass BH (100-100,000 Msun), which would be a revolutionary discovery, even if one event is detected. The data will be also valuable for the geometric distortion calibration for the other Roman observations. Our team is developing the astrometric analysis tools for JASMINE and ULTIMATE-SUBARU, and we wish to work with the other astrometry experts in the Roman community to maximise the synergies of these upcoming novel and unique NIR facilities.
Galactic Bulge Time Domain Survey stellar populations and the interstellar medium Stellar Populations: Astrometry Stellar Populations: Galactic center, Stellar Populations: Galaxy evolution, Stellar Populations: Gravitational microlensing, Stellar Populations: Star clusters
Daisuke Suzuki Osaka Univeristy Naoki Koshimoto(NASA Goddard/UMD), Shota Miyazki(ISAS/JAXA), Takahiro Sumi(Osaka U) Black Hole Microlensing Survey with Roman and ULTIMATE-Subaru toward the Galactic Center We propose to observe the Galactic center region (|l|<0.5 deg and |b|<0.4 deg) by using F213 filter with a cadence of at least every 5 days (TBD, higher the cadence is the better) to find and characterize the black hole (BH) microlensing events. Although some BH microlensing events are expected to be found by the Roman Galactic Exoplanet Survey in their nominal survey bulge field that are not including the Galactic center, the proposed observational field includes the nuclear stellar disk whose population could be different from those of the bulge. We will use both photometric and astrometric information for the light curve and astrometric microlensing signals to find/characterize the BH microlensing events.

This can be done only by the instruments with wide FOV, high angular resolution and K-band filter, because this area is a relatively large, very dense, and highly obscured region by the interstellar dust.

This field will be observed by the ground-based NIR PRIME telescope and Japanese NIR astrometry mission, JASMINE. But, PRIME is seeing-limited and uses H-band, and JASMINE can detect only bright stars for the very precise astrometry measurement. ULTIMATE-Subaru will also monitor the Galactic center with GLAO (14' x14' FOV and ~0.4" seeing) and K-band to find the BH microlensing events, which will be a powerful survey program if realized, but the Galactic center is only visible in summer from Hawaii. By combining the Roman data, these survey data become highly valuable, because the light curve coverage is complementary to each other to measure the satellite and orbital parallax signals and to constrain the astrometric microlensing signals. ULTIMATE-Subaru will be online in late 2020s, but precursor Roman observation will be important especially to measure the astrometric microlensing signals.
Galactic Bulge Time Domain Survey stellar physics and stellar types, stellar populations and the interstellar medium Gravitational microlensing,
Dan Maoz Tel Aviv University Radek Poleski (Astronomical Observatory, University of Warsaw) 1000 Supernovae projected behind the Galactic bulge: detecting interactions with companions and circumstellar material in continuous very early SN light curves Our current understanding of the explosion physics and the progenitors of the various supernova (SN) types is rudimentary, at best. It has long been realized that deep, high-cadence, photometry of the very early phases (minutes to hours) of the explosions could provide deep insights regarding both issues. Such data would allow detecting, e.g., shock breakout from the surface of the progenitor stars, and signatures of interaction of the SN ejecta with either stellar-binary companions or with the pre-explosion circumstellar matter. However, to date such early data (usually quite noisy) has been obtained only for a handful of SNe. The design of the Roman Space Telescope as a deep SN discovery engine, combined with the Roman Galactic Bulge Time Domain Survey (RGBTDS), with its continuous, high cadence (15-20 min) photometry will be a game changer in the discovery and analysis of SN light curves immediately upon their "first SN light". We propose to discover and analyze the behind-the-buge SNe from the RGBTDS data. Extinction through the full bulge in the RGBTDS footprint for the wide-band F146 filter is between 0.5 and 2.0 mag (depending on wavelength). Considering the extinction, the survey strategy, and the SN rate (based on optical and IR surveys for SNe with HST), we estimate RGBTDS will discover of order 1000 SNe. A significant fraction of them will have light curves with sufficient signal-to-noise for the proposed study. Galactic Bulge Time Domain Survey stellar physics and stellar types, stellar populations and the interstellar medium massive stars, supernovae, white dwarf stars, binary stars, circumstellar matter
Daniel Yahalomi Columbia University David Kipping Transit Timing Variations and White Dwarf Transiting Exoplanets with Roman Photometry The Roman Galactic Bulge Time Domain Survey will observe 56 million stars down to H_AB = 21.6 for five-years. Each data point will consist of a single ~52-second observation taken during six 72-day campaigns with a 15 minute cadence. This survey will observe two orders of magnitude more stars than Kepler, leading to an estimated 10^5 transiting exoplanet detections (Montet et al. 2017). As Roman will observe many faint stars, most of these stars cannot be followed up by ground based radial velocities for confirmation. Therefore, confirmation via observation of secondary eclipses and transit timing variations (TTVs) will be essential for the Roman transit detections. Although large data gaps will complicate the analysis of any TTVs, we can expect them to be less affected by starspots than those obtained by Kepler, thanks to the near-IR bandpass. Montet et al. (2017) show that 20-30 minute TTV precision can be expected, making dozens of known TTV systems detectable (e.g. Kepler-88b/c Nesvorny et al. 2013). We thus expect precise masses to be degenerate from WFIRST TTVs, but planet confirmation feasible. Further, long-term monitoring of both known and new hot-Jupiter systems will constrain/detect tidal inward migration, manifesting as a secular period change. Accordingly, Roman can have a large impact in TTV science from a demographics perspective.

Additionally, we believe that a search for transiting exoplanets with white dwarf (WD) hosts in the Roman Galactic Bulge Time Domain Survey could be quite fruitful. Roman will detect ~10^6 WDs, including the coolest and most ancient WDs, as well as those with debris disks (Fantin et al. 2020). Van Sluijs and Van Eyken (2017) investigated 1182 WDs in the K2 dataset in search of planets and other substellar bodies, placing upper limits on the occurrence rate of hot-Jupiters (<1.5%) and habitable zone Earth-sized planets (<28%). Vanderburg et al (2015) estimate that the transit probability for disintegrating planets is ~2%. Using these values, we can place a somewhat naive upper limit on expected yield of such a survey - assuming 10^6 WDs, a conservative upper limit occurrence rate of 10% WDs with planets, and 1% transit probability - this study could produce up to 10^3 WD transiting systems and if not would provide new constraints on WD planet occurrence rates. This recovery rate is consistent with Vanderburg et al (2020), which presented a single transiting WD in TESS data from a search of several thousands candidates. For WDs detected by Roman in the galactic bulge time series survey, the relatively fast exposure time (~52 seconds) would aid in obtaining precise transit models for exoplanet transits in front of WD hosts, which have short ~several minute to ~several tens of minutes durations. One difficulty will be that the Roman cadence is 15 minutes. However, as presented in Cortes and Kipping (2019) for simulated LSST WD transits, we care about phase coverage, rather than temporal coverage, in searching for transits. Assuming the observational program described above, each star will be observed 72 days/15 minutes or 6,912 times per campaign. With a five-year observing program and six 72-day campaigns performed before repeating the tiling, each campaign area will be observed on average 4.225 times. Therefore, on average, each star in the bulge will be observed 29,200 times. We propose that you could recover WD transits via the following procedure: (1) pick a possible orbital period of the transiting planet, (2) phase fold these 29,200 observations on that given period, and (3) perform a box-least squares fit to determine if a transit is consistent with the phase-folded observations at that given period. By sampling a wide range of transiting periods, one could then search for WD transits. As phase-folding and fitting a box-least squares fit is relatively computationally inexpensive, one could perform this operation on a large number of possible periods in order to sample the entire period parameter space. There is currently one known example of an exoplanet transiting a WD (Vanderburg et al. 2020) and searching for more WD exoplanet transits will provide crucial information for planets around stars at the end of their lifetimes. Roman will provide a unique opportunity to do so, with its high precision photometry for faint stars, long duration, and large observational fields leading to a large number of observable WDs.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation Exoplanets, Exoplanet detection methods, Transits, White Dwarfs
Eamonn Kerins University of Manchester, UK A survey for potentially habitable Earth-sized planets located within the Earth Transit Zone Low-mass stars are the most common stars in our Galaxy and are known, locally, to have a high abundance of Earth-sized planets within their habitable zone (HZ). With a 1-2 month transit survey of a single Roman field there is an opportunity to extend our knowledge of the occurrence of Earth-like planets ("eta-Earth") around the most common stars out to much greater Galactic distances. A roman field centred at Galactic coordinates l=6.4 deg, b = 0 deg will cover the most densely populated region of the Earth Transit Zone (ETZ). The ETZ is a thin band centred on the Ecliptic Plane from where observers on other planets would have a view of Earth as a transiting planet. This region has relatively high optical extinction and so Roman's near-IR capabilities will be essential. Transiting planets within the ETZ are recognized as being of special interest in the Search for Extra-terrestrial Intelligence (SETI) and this survey sample would provide the first SETI-optimized list of candidate HZ planets for targeted SETI follow-up. To achieve this it would be necessary to place this field at a somewhat offset position from the rest of the GBTDS fields, for the duration of 1-2 months. Whilst this would slightly lower the overall microlensing exoplanet yield, it would provide a different directional probe through the Galactic disk and bulge. The resulting differences in the observed stellar microlensing distribution would help to improve our knowledge of the inner Galactic structure, which in turn would help improve the reliability of inferred microlensing exoplanet demographics from the GBTDS. Galactic Bulge Time Domain Survey exoplanets and exoplanet formation, stellar populations and the interstellar medium, galaxies Exopolanets, SETI, Galaxy structure, Galaxy bulges, Galaxy disks
Jan Skowron Astronomical Observatory, University of Warsaw Brown dwarfs and planets in multiple systems Stars are often found to be members of multiple systems. We expect that many of the systems detected in the Roman microlensing survey of the Galactic bulge will have additional companions. The most interesting multiple systems are the ones we know the least about: systems with brown dwarfs, planetary systems and multiple brown-dwarf systems. Although the microlensing signal from the stellar-mass object is often strong and long lasting, the signal expected from a brown-dwarf or a planetary companion usually has much shorter timespan. Even if one companion to the main host star would be in a favorable position to be detected with relatively sparse photometric coverage, the other companion most likely would not. Its presence would be typically noticeable only during a short fraction of the light curve - due to less favorable geometry and low mass. In order to maximize the chance of discovering multiple low-mass companions it is required to conduct a survey that is both continuous and high-cadence.

Most of the microlensing events with such favorable geometries that will allow us to discover multiple systems will have, due to statistics, an M-dwarf star as a background source. Such a star, having a radius of ~0.1 Solar radii, will have its radius crossed by the lens in ~5 minutes and thus, will let us detect very low-mass companions, provided that we sample the light curve with similar cadence. The Roman Galactic Bulge Time Domain Survey will be monitoring 7 fields every 15 minutes. The main goal is to measure the statistics of the planetary systems and thus, the survey is constructed to maximize the size of the sample. I propose to dedicate one of the fields to be a double-cadence field (i.e. cadence of 7.5 minutes). This would not decrease the number of discovered planets much, but it would expand the parameter space of the discovered planetary systems and has a potential to yield additional families of multiple systems to the Roman sample, like multiple brown-dwarf and multiple planetary systems.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation Brown dwarf stars, Exoplanet systems, Natural satellites (Extrasolar), Gravitational microlensing
Jan Skowron Astronomical Observatory, University of Warsaw More consistent color measurements of the microlensing source stars During the Galactic Bulge Time Domain Survey it is planned to continuously monitor microlensing events in a single wide band (F146) to measure the basic light curve parameters. It is stated that the 7 fields will be monitored in a bluest filter for one exposure every 12 hours in order to measure the color of the microlensing source stars. The bluest filter is F062. While this strategy is sufficient to measure colors of G and K stars, it might be problematic for the large number of microlensing sources, i.e. M-dwarf stars. In order to facilitate even better measurements of masses of the discovered exoplanets, I propose a slight change in this strategy.

The spectral energy distribution of M dwarfs peaks within the F146 wide filter and falls rapidly toward shorter wavelengths. Additionally, significant extinction is present in the monitored fields further diminishing any signal in the F062 filter. Most of the M-dwarf source stars will be blended with the M-dwarf lenses. All these factors yield very low signal-to-noise measurements of the colors of source stars. A much better choice for the M-dwarf would be a F087 filter, however, the separation between its wavelength and the wide-band filter is not sufficient, leading to weak leverage for the measurement for all stars. I propose to add occasional exposures in one of the red filters of standard width, for example F158, as well as F087. A pair of F087 and F158 measurements would yield high signal-to-noise color measurement for M-dwarfs. The measurements in F062 will allow for better characterization of hotter stars. The sub-1-day cadence in one of the filters is preferable in order to get the color information for the shortest events, however is not necessary in all filters. The additional color information (in one red and another blue filter) gathered every 1-3 days would benefit the great majority of events and will not interfere with the main survey goals. Such additional, continuous color data will also benefit other astrophysical studies in the time domain.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation, stellar physics and stellar types Exoplanets, Exoplanet detection methods, Free floating planets, Variable stars
Jens Hoeijmakers Lund University, Sweden This science idea is supported by a number of colleagues at Lund observatory interested in time-domain photometry of globular clusters and the Nuclear Star Cluster. Transiting exoplanets in dense cluster environments A defining feature of the gas giant exoplanet population is a correlation between stellar metallicity and gas giant occurrence rate, hypothesised to be caused by the availability of heavy elements in the protoplanetary disk needed to form rocky cores large enough to trigger runaway gas accretion. The stellar environment may play an important role in determining the outcome of planet formation, although the details are only understood circumstantially. To elucidate planet formation processes, many exoplanet-finding surveys have targeted stars in environments other than the solar neighbourhood, including stellar clusters, young stars, evolved stars, bulge stars and halo stars.Several transit surveys of globular clusters (GCs) have been carried out, including 47 Tuc, M4, M71 and NGC 6397. Each of these covered thousands to tens of thousands of stars and were sensitive to Jupiter-sized planets in short-period orbits of up to 5 days. None of these surveys have succeeded in detecting a single hot Jupiter. It has been argued that this is because GCs consist of old stars that are too metal-poor to efficiently create hot Jupiters and that low metallicity may constitute a fundamental inhibitor to hot Jupiter formation. At the same time, these results have been disputed on the grounds of statistical rigour: Relatively short survey durations covering up to 10,000 stars has been argued to be insufficient to significantly rule out a hot Jupiter occurrence rate equal of that of the field (Masuda & Winn 2017). Moreover, dense cluster environments may also be conducive for hot Jupiter formation. Hamers & Tremaine (2017) show that stellar encounters may convert 1%-2% of planets systems into hot Jupiters via high-eccentricity migration, while ejecting many others. This would result in a significant increase of the hot Jupiter fraction compared to the galactic disk (i.e. elevated by a factor of 2 to 3). Close stellar encounters may also induce orbital decay of already close-in planets, and once migrated inwards, short-period planets remain bound to their host stars over Gyr timescales even in dense clusters. Two clusters are of particular interest: Omega Centauri and the Nuclear Star Cluster host stars with varying metallicities, potentially allowing planet formation to take place in these environments.

We propose that the WFI on Roman provides the perfect opportunity to carry out surveys of cluster environments in search of transiting planets. The most impactful cluster survey was done with HST targeting a very narrow field in 47 Tuc (Gilliland et al. 2000). The much wider FOV offered by the WFI would enable instantaneous coverage of an entire cluster (typical diameter of up to 1 square degree), and orders of magnitude more stars. Several bright, nearby clusters exist that could be targeted by the core community surveys, including 47 Tuc and Omega Centauri, which at declinations of -72 and -47 may be covered in pointings as part of the High Latitude Time Domain Survey (but would require a higher cadence, of ±30 minutes). The Nuclear Star Cluster could be covered by adding a galactic center field to the Galactic Bulge Time Domain Survey (with the W146 filter sensitive up to 2 microns). The cadence of <15 minutes offered by the Galactic Bulge survey is perfectly suited for transit observations (as already explored by Montet et al (2017). In this way Roman could discover the first transiting planets in the galactic center; while providing a wealth of ancillary data for time-domain photometry of the galactic center (e.g. variable stars) and complementarity with JWST which is scheduled to observe deep galactic center fields as well.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation Transits, Exoplanets, Extrasolar gas giants, Exoplanet formation
Kailash Sahu STScI Detectiong Isolated Stellar Mass Black Holes with Roman Isolated Stellar-Mass Black Holes (ISMBHs) are potentially discernible with Roman through their astrometric signals. Sajadian and Sahu (2023, Astron. J. 165, 96) recently carried out a large simulation of microlensing events as seen by Roman, and calculated the resulting errors in the physical parameters of the lenses, including their masses, distances, and proper motions. Their simulations confirm that Roman should indeed detect a large number of ISMBHs and measure their physical parameters. However, the ~2.3-year time gap between Roman's first three and the last three observing seasons lowers the efficiency of detection and introduces significant uncertainties in the derived physical parameters of the ISMBHs.

As shown by Sajadian and Sahu (2023), the situation can be significantly improved by adding a small amount of additional observations -- about 1 to 2 hours (for 4 to 8 astrometric measurements) every 10 days when the Bulge is observable during the large time gap. Since the expected timescales of the events caused by ISMBHs are long (> 150 days), additional observations every 10 days will be adequate to fully characterize these events. These additional observations amount to an equivalent of a total of one to two additional days of observations with the Roman telescope. These extra observations increase Roman's efficiency for characterizing ISMBHs and, more importantly, improve the robustness of the results by avoiding possible degenerate solutions (see Sajadian and Sahu 2003, for full details.)

There is considerable interest in the astronomical community for detecting and measuring the masses of ISMBHs. Roman provides the best, perhaps the only, possibility of deriving the mass function of ISMBHs in the near future through detection of a large number of such objects. Accordingly, we recommend adding one to two hours of observations of the microlensing fields every 10 days when the Bulge is observable during the ~2.3 year time gap. The total time needed is an equivalent of 1 to 2 days--clearly a very small investment for the huge expected return.
Galactic Bulge Time Domain Survey stellar physics and stellar types n/a
Kishalay De Massachusetts Institute of Technology Revealing the obscured and dynamic Galactic bulge with a wide area survey Stellar variability forms one of the corner stones of modern astronomy. From stellar pulsations in the smallest white dwarfs to ellipsoidal variability in the largest giants, optical time domain surveys combined with the unprecedented astrometric capabilities of missions like Gaia are revolutionizing our understanding of stellar life cycles and populations -- essentially re-writing textbooks underpinning every area of astrophysics. Yet current optical datasets remain severely limited in terms of understanding Galactic scale demographics of variability, as well as finding rare stages in stellar evolution due to the extremely small accessible volume in the dust obscured Galactic plane. Only in the last few years have shallow infrared time domain surveys from the ground begun to unravel this hidden landscape of variability, with infrared time domain datasets expected to grow exponentially by the time of start of the Roman mission.

The Roman space telescope's Galactic bulge time domain survey is poised to be a game changer in our understanding of exoplanet demographics via microlensing searches. Yet, the exceptional infrared sensitivity and spatial resolution of the same surveys can revolutionize the field of stellar astronomy with minor modifications to the survey design aimed at increasing the effective stellar mass footprint. As the exact footprint of the Roman Galactic Exoplanet Survey remains to be confirmed, we recommend that the survey covers a large footprint than the planned 2.0 sq. deg. patch in the Galactic bulge (Penny et al. 2019). This could be achieved, for instance, by lowering the average cadence in the footprint, or by selecting a wider patch (~ 10 sq. deg.) meant for lower cadence monitoring (~ 1 day). We stress that even lower cadence data on this extremely rich (but yet optically inaccessible due to dust obscuration) stellar fields near the Galactic center will provide a golden dataset for stellar astronomy, revealing clues to historic unanswered questions ranging from the population of low frequency gravitational wave sources like close binary white dwarfs (e.g. Burdge et al. 2019), close binaries on their approach to merger (e.g. Tylenda et al. 2011) to hidden black holes lurking around luminous companions (e.g. El. Barry et al. 2022). This dataset will be ideally placed to capitalize on synergies with ongoing and near-future shallower surveys in the infrared (e.g. PRIME, WINTER, DREAMS, Gattini-IR) as well as the upcoming Vera Rubin Observatory.
Galactic Bulge Time Domain Survey stellar physics and stellar types, stellar populations and the interstellar medium Binary stars, evolved stars, variable stars, neutron stars, stellar evolution
Kumiko Morihana NAOJ Masahiro Tsujimoto Search for faint Cataclysmic Variables at Galactic Bulge The Galactic Diffuse X-ray Emission (GDXE), which is apparently diffuse X-ray emission of a low surface brightness along the Galactic Plane, has been known since 1980s, but its nature has been a mystery for a long time. One theory of the origin of the GDXE considered that the GDXE is a sum of faint X-ray sources such as Cataclysmic Variables (CVs) and late-type stars based on X-ray properties. At the Galactic Bulge, Chandra X-ray Observatory resolved ~80% of the GDXE into faint X-ray point sources (Revnivtsev et al., 2009). However, it is difficult to constrain the nature of these point sources from X-ray data alone due to a lack of X-ray photons. Follow-up observations with longer wavelengths such as NIR imaging and spectroscopy have been carried out and the nature of some of these point sources was revealed, which are magnetic-CVs, non-magnetic CVs with high accretion rate, and non-magnetic CVs with low accretion rate (Morihana et al., 2016, 2021). However, the spatial density of CVs estimated from H-alpha survey (e.g., 10^−6 pc^−3; Patterson et al., 1998) is smaller than the theoretically predicted value (e.g., 2×10^−5 pc^−3, Politano et al., 1996). The population evolution model also predicts that most white dwarf binaries will be faint with a low accretion rate (e.g., Howell et al., 2001). Therefore, there are still undiscovered faint CVs hidden on the Galactic bulge.

Then, we propose to search faint X-ray binaries, especially CVs, at Galactic Bulge using the data of 7 fields of the Galactic Bulge Time Domain Survey of the Nancy Grace Roman Space Telescope. The 7 fields (a total of ~2 deg^2) planned to observe by the Roman telescope already had been observed by Chandra X-ray observatory and detected faint X-ray point sources (e.g., Revnivesev et al., 2009, Morihana et al., 2013, van den Berg et al., 2009). To search CVs efficiency, we focus on that CVs are known to have hydrogen recombination lines such as Pa-beta (1.282 μm), Pa-alpha (1.875 μm), and Br-gamma (2.166 μm) with equivalent widths of about -10 to -170 angstrom in their NIR spectra (e.g., Dhillon et al., 1995, 1997, 2000) and CVs have time variability with 1-2 hour period even on quiescence. Thus, we can pick up CVs with repeated observations using narrow-band filters that have a transmission on the recombination lines. We would like to use F184 or F129 filters to search faint CVs at the Galactic bulge. Since the equivalent width of emission lines of Pa-alpha is 1.5-2 times more than other hydrogen recombination lines for known CVs (e.g., Dhillon et al., 2000), F184 is more suitable than F129 for our purpose. Combination the repeated observation data of FW184 (every 6 hours; page 7 of or FW129 (every 12 hours: with X-ray hardness, we search faint CVs at the Galactic bulge.
Galactic Bulge Time Domain Survey stellar populations and the interstellar medium Binary stars, White dwarf stars, Variable stars
László Molnár Konkoly Observatory, CSFK, Budapest Csaba Kiss, Róbert Szabó Surveying the rotational properties of TNOs Despite three decades of discoveries, we still know very little about the rotational properties of trans-Neptunian objects. Recent results from the Kepler space telescope by Kecskeméthy et al. (2023) have shown that ground-based rotation rates rarely agree with those inferred from space-based photometry. Kepler observed nearly 70 TNOs during the K2 mission, but many of them were at the telescope's detection limit, down to 23 magnitudes, so rotation rates could only be determined for about half of them. Nevertheless, the continuous light curves showed that many objects have rotation periods of a few days, much longer than what could be detected by ground-based observations.

With Roman's much higher sensitivity and resolution, coupled with a cadence and campaign length similar to K2, we expect it to discover and characterize a large number of TNOs at a much smaller size, despite its smaller field of view. Roman will allow us to measure rotation light curves to a much higher precision than Kepler, which will inform us not only about periods, but also about the shape characteristics of TNOs down to the 100 km diameter range. It will also be able to measure rotation rates for an unbiased sample of small TNOs, in the 10-100 km range, for the first time.
Galactic Bulge Time Domain Survey solar system astronomy Trans-Neptunian objects, Small solar system bodies, Binary systems / Multiple systems
László Molnár Konkoly Observatory, CSFK, Budapest Csilla Kalup, Rozália Ádám, Róbert Szabó Deep survey and asteroseismology of obscured Galactic globular clusters The bulge is home to many globular clusters. A number of them are far away or obscured by dust. Some of these have been discovered only recently, and a few of them have never been studied in detail, although they are expected to contain various types of variable stars, just like their brighter counterparts. However, as results from ground-based and space-based time series photometry show, variable stars such as the RR Lyrae population of the cluster, blue stragglers, eclipsing binaries, and oscillating red giants provide a wealth of information about the cluster. These include photometric metallicities (of the RR Lyrae stars), constraints on the formation of eclipsing binaries, mass loss histories, or distance estimates.

In particular, the Kepler space telescope has shown that longitudinal observations of globular clusters can be very valuable. Seismic parameters could be derived for giants in the cluster M4, which was also the target of an extensive variability search. Upcoming work on other K2 clusters (M80, NGC 5897) will show how precise photometry of cluster RR Lyrae stars can be used to obtain detailed pulsation profiles and signatures for these stars, allowing us to estimate their physical parameters. Roman could achieve similar success but its more powerful optics and infrared filter would make it possible to target the obscured and/or distant clusters around the bulge, too. Furthermore, multicolor photometry, especially at the turn-off point, the main sequence, and the normal and extreme horizontal branches, can be used to unravel the star formation history of a cluster. Placing the fields of the Bulge survey, either in the nominal mission or during an extension, in such a way that they encompass one or more clusters will give us a truly unique opportunity to study globular clusters in these ways.
Galactic Bulge Time Domain Survey stellar physics and stellar types, stellar populations and the interstellar medium Globular star clusters, Variable stars, Star formation, Population II stars
László Molnár Konkoly Observatory, CSFK, Budapest Róbert Szabó Asteroseismology of lensed stars in the bulge Microlensing events magnify the stellar source by 10 to 1000 times its normal brightness, briefly bringing it within the range of instruments that would otherwise not be sensitive enough to detect it. This can be exploited in a variety of ways, such as recording the spectra of magnified dwarf stars within the Galactic Bulge. Photometric observations, on the other hand, allow us to detect the variability of the source if the lensing event is slow enough. Einstein timescales of Bulge microlensing events range from a few days to about a hundred days, with an average of 22 days. Longer events thus have the ability to significantly magnify the source for a few weeks. This is comparable to a 27-d observation in a single TESS sector, and single-sector data have been used to determine seismic parameters of stars in that mission.

Many parameters will determine whether Roman is able to extract seismic information for a lensing source. However, given enough amplification, the 15-minute cadence of the Bulge survey and the limited amount of time a source is sufficiently magnified can give us an idea of what sources to expect. Stars with lower oscillation frequencies will have higher amplitudes, but short observations will be limited to frequencies of maximum amplitude (nu_max) above a few to 10 microHz. The cadence gives us an upper limit of a few hundred microHz, but at high values the mode amplitudes are also much lower and may not be detectable at all. Based on the TESS single-sector observations analyzed by Stello et al. (2022), red clump stars are best suited for observations: they are sufficiently bright and their oscillations are in the right range with nu_max values around 30-40 microHz. Further simulations would certainly be needed to calculate a realistic yield for Roman observations: however, any seismic detection of a Bulge star would be a significant achievement for the Roman space telescope.
Galactic Bulge Time Domain Survey stellar physics and stellar types Variable stars, Evolved stars, Gravitational microlensing
László Molnár Konkoly Observatory, CSFK, Budapest Susmita Das Precision photometry and seismology of pulsating stars across the Milky Way Classical pulsating stars are extremely important distance estimators because of their well-defined period-luminosity (PL) relations. However, at present, one of the primary hindrances in the precise calibration of the PL relations arises from the inability to accurately determine the effect of metallicity on the PL relations. RR Lyrae stars offer us the advantage of estimating their metallicities from their light curve structures, which in turn requires precise photometric data.

To this end, the simultaneous and precise photometry and spectroscopy of RR Lyrae stars in the Milky Way from the Nancy Grace Roman Space Telescope would prove crucial in the comparison of the photometric and spectroscopic metallicities of the particular stars. Photometric metallicity estimates can be calibrated from known or measured spectroscopic values, and then estimates can be given for stars that are too faint for spectroscopy, well within obscured regions or at large distances. The derived period, brightness and metallicity values can then be used for a precise calibration of the period-luminosity-metallicity (PLZ) relation.

Furthermore, precise, high-cadence photometry of classical pulsating stars can reveal a multitude of low-amplitude modes, providing us with detailed seismic signatures. Some of these modes are understood well enough to be modeled, and can be used to infer physical properties for classical pulsating stars. Continuous light curves from Roman will make it possible to determine the intrinsic variability of these modes and to compare them to the long-term observations of the OGLE survey. Roman will also allow us to survey seismic signatures of pulsating stars deep within the bulge and on the far side of the Milky Way, far outside the reach of the Kepler and TESS space telescopes.
Galactic Bulge Time Domain Survey stellar physics and stellar types, stellar populations and the interstellar medium Variable Stars, Stellar abundances,
Makiko Ban University of Warsaw, Astronomical Observatory Search for free-floating planets via double-lens events Roman is expected to find more exoplanets including free-floating planets (FFPs). A fundamental question to determine FFPs is whether the planet is just orbiting at a wide semi-major axis (i.e. physically bound) or floating alone. Here, we have an idea that there might be a planetary microlensing event that is mimicking a binary-lens event whilst the event is actually offered by two physically unbound lenses (we call it a "double-lens" event hereafter). According to our simulation, about 4% of stellar microlensing events may overlap with the Earth-mass FFP event under the assumption that the Earth-mass FFP population is 10 times larger than that of the main-sequence (MS) stars. This percentage is a theoretical value from the optical depth and threshold magnification to yield a microlensing alert as a single-lens event for each Earth-mass FFP and MS star case. We also confirmed from our simulation of the double-lens event that the compilation of two lenses helps to make the FFP microlensing effect observable even though the magnification is not enough to alert as a single-lens event. That is to say, the detectability of Earth-mass FFPs may increase.

The planetary event data collected throughout the Roman exoplanet campaign is useful to search for the double-lens event by FFPs. The detailed simulation for the double-lens event is ongoing to find any keys to distinguish between binary- and double-lens events. This research also helps to estimate the boundary of the physical connection of the wide-orbit planet. The probability of the double-lens event still has an uncertainty on the population of bound planets and FFPs. Even though no double-lens events are found in Roman data, the fact assists to proceed with the FFP population research.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation Astronomical simulations, Exoplanets, Free floating planets
Marc Pinsonneault Professor of Astronomy, the Ohio State University Tim Bedding (U Sydney), Scott Gaudi (OSU), Marc Hon (U Hawaii), Daniel Huber (U Hawaii), Matthew Penny (LSU), Sanjib Sharma (Johns Hopkins), and Dennis Stello (UNSW) Asteroseismology in the Galactic Bulge Red giants oscillate, and these oscillations can be used as powerful diagnostics of global stellar properties. Time domain surveys from space - CoRoT, Kepler, K2 and TESS - have been able to characterize these asteroseismic properties in large samples of stars. However, other missions are limited to relatively nearby, bright targets (because of small apertures) or uncrowded fields (due to large pixels). The Roman Galactic Bulge Time Domain Survey is well-suited for asteroseismology of the crucial, and poorly understood, stellar populations in the center of the Galaxy. Oscillations will have lower amplitude in the IR than the visible, but they should still be detectable. The high spatial resolution of Roman, its relatively large aperture, and the ability to see deep into the Galactic center at infrared wavelengths all make Roman a potent engine for studying stellar populations that are not accessible with other time domain surveys. Ultra-precise astrometry will give powerful independent constraints on asteroseismic masses and radii, and complementary information from stellar granulation may also be obtainable. The notional cadence, area, and dwell of the Galactic Bulge Time Domain Survey are reasonably well-matched to those required for asteroseismology. However, some modification of these and other survey parameters may enable additional transformative stellar science.

Masses from asteroseismology can allow us to measure the distribution of ages; when combined with spectroscopic and astrometric surveys, we can also reconstruct the chemical and kinetic evolution of our bulge, permitting a much more complete picture of the formation and evolution of the Milky Way Galaxy. This program will therefore have synergy with other survey science, such as interpreting transit and microlensing demographics or stellar remnant mass functions.
Galactic Bulge Time Domain Survey stellar physics and stellar types, stellar populations and the interstellar medium Galaxy bulges, Late-type stars, Stellar evolution, Stellar abundances, Variable stars
Matthew Digman Montana State University Chris Hirata Multi-messenger White Dwarf Binaries in the Galactic Bulge Time Domain Survey Short-period Galactic white dwarf binaries detectable by LISA are the only guaranteed persistent sources for multi-messenger gravitational-wave astronomy. Large-scale surveys in the 2020s present an opportunity to conduct preparatory science campaigns to maximize the science yield from future multi-messenger targets. The Nancy Grace Roman Space Telescope Galactic Bulge Time Domain Survey will (in its Reference Survey design) image seven fields in the Galactic Bulge approximately 40,000 times each. Although the Reference Survey cadence is optimized for detecting exoplanets via microlensing, it is also capable of detecting short-period white dwarf binaries. In a recent paper entitled "LISA Galactic Binaries in the Roman Galactic Bulge Time-Domain Survey" (arXiv:2212.14887), we presented conservative forecasts for the number of detached short-period binaries the GBTDS will discover, and the implications for the design of electromagnetic surveys. Although population models are highly uncertain, we found a high probability that the baseline survey will detect of order ~5 detached white dwarf binaries. The Reference Survey would also have a >20% chance of detecting several known benchmark white dwarf binaries at the distance of the Galactic Bulge.

One consideration for optimizing the GBTDs for binary white dwarfs is ensuring that the visits to the individual fields are not precisely periodic to mitigate aliasing. A survey more specifically optimized for detecting binary white dwarfs would also include some continuous blocks of higher-cadence exposures of individual fields, rather than slewing between the fields for every exposure.
Galactic Bulge Time Domain Survey stellar physics and stellar types, stellar populations and the interstellar medium Binary stars / Trinary stars, White dwarf stars, Neutron stars, Stellar populations, Stellar evolution
Naoki Koshimoto University of Maryland, College Park Takahiro Sumi, Daisuke Suzuki, Shota Miyazaki Constraints on lens masses for several thousands of past microlensing events including ~100 planetary systems and dozens of candidates for free-floating planets and black holes One of the primary mass measurement methods in the Roman microlensing survey is high-angular-resolution imaging of lenses that are far enough away from the source to be resolvable by allowing time after magnification. However, due to the limitation of the 5-year baseline for the Roman GBTDS, this method can only be applied to events where the relative lens-source proper motion is larger than a certain degree among the events Roman will discover. On the other hand, the ground-based optical wide-field survey toward the Galactic bulge, which began in 2006, has found more than 10,000 events to date. Most of the lenses will be far enough away from the source to be resolvable by Roman by 2026.

We propose to conduct two epochs of observations at the beginning and the end of the GBTDS each with F087- and F184-bands fo a 10 - 20 deg^2 (TBD) region of the bulge where several thousands of past events reside to constrain the lens masses. This will add up to ~100 more planetary systems (and thousands of stars) with mass measurements by using 6-12 hours (TBD) of Roman's observation time. Observations in the two separated epochs help us determine a pair of source and lens by measuring the vector of the relative proper motions. The F087-band observation helps us identify the source star because the source magnitude in I-band is known from the ground-based observation, while the F184-band observation is to detect the lens stars that are expected to be redder than the source stars. Multiband observations will also allow us to measure the color-dependent centroid shift, enabling us to measure the lens mass even for events where the lens is yet to be resolved from the source. The multiband observations should be taken almost simultaneously in each epoch for the centroid shift measurements. The targets include not only ~100 bound planetary systems where mass measurements are expected for the majority of them, but also dozens of black hole candidates and free-floating planet candidates where their darkness can be verified by the observations.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation, stellar physics and stellar types, stellar populations and the interstellar medium Gravitational microlensing, Exoplanets, Free floating planets, Stellar populations
Patrick Tamburo Boston University Philip S. Muirhead, Courtney D. Dressing The Galactic Bulge Time Domain Survey will Detect Thousands of Small Transiting Planets around Mid-M and Ultra-Cool Dwarfs By detecting thousands of transiting exoplanets, the Kepler space telescope measured the occurrence rates of short-period planets for many different stellar types. Planet occurrence rates allow us to predict the number of planets of a certain type (e.g., within a given radius and orbital period range) given the properties of a host star (e.g., mass or metallicity), and the results from Kepler revolutionized our understanding of the architecture of typical planetary systems in our Galaxy. However, due to its optical bandpass (0.40-0.85 μm), Kepler lacked the sensitivity to detect significant numbers of transiting exoplanets around the latest spectral types. The planet populations around mid-M dwarfs (~M3-M7) and ultra-cool dwarfs (UCDs; M7 and later) are, as a result, almost entirely unconstrained. This "final frontier" of short-period planet occurrence rates is unlikely to be explored by the TESS mission, which, despite using a redder bandpass (0.60-1.00 μm), has a much smaller aperture than Kepler (10 cm vs. 95 cm). While dedicated ground-based surveys have begun exploring this parameter space and have made impactful discoveries (e.g., the seven-planet system around TRAPPIST-1), they would have to detect hundreds of planets to determine occurrence rates to a similar precision as measured for earlier spectral types with space-based wide-field surveys.

The Nancy Grace Roman Space Telescope, with its broad near-infrared wavelength coverage, large aperture, and wide field-of-view, represents the first large-scale mission with the capacity to pin down small planet occurrence rates around mid-M dwarfs and UCDs. The Galactic Bulge Time Domain Survey will target hundreds of thousands of these sources, and we predict that it will permit the detection of thousands of small (Rp < 4 R⊕) transiting exoplanets around M3 spectral types and later, more than an order-of-magnitude increase over the current number of known small planets around these host types (Tamburo et al., in prep.). These detections, in turn, will calibrate planet formation models, which currently predict a diverse array of planet formation outcomes around very low-mass stars and brown dwarfs. This understanding is critical, as transiting planets around the latest-type stars are the only planets whose atmospheres can be characterized with current and near-future observatories.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation, stellar physics and stellar types Exoplanets, transits, low mass stars, planet hosting stars, extrasolar rocky planets
Premkumar B. Saganti Prairie View A&M University None CMOS Sensors as Radiation Detectors During the past five years, we developed two innovative space radiation payloads. Our 1st payload was launched in 2014 (Shinen2) into deep space around the Sun between Venus and Mars orbits [1]. Most recently, we designed and developed our 2nd payload for Ten-Koh Spacecraft that was launched into Earth's polar orbit in 2018 and our data / results are very promising as of this writing including our first x-ray measurements [2]. Our most recent payload is very light weight (~ 600 gr), operates with very low power (~ 2W), having a very low volume (~ 1U), and very low data rate (few kb via radio waves). In this proposal, we plan to expand our payload (to ~ 1kg, 3W, 2U, 1Mb) and increase the ability to address one of the prime challenges - the radiation risk assessment for human explorations beyond earth's orbit (a priority for NASA's human exploration to the deep-space), in lunar orbit and lunar surface [3-6].

We believe and suggest including a dedicated radiation measurement detector system as we did for the other spacecrafts for the exclusive radiation data collection will improve the operation and authenticity of the collected data. By incorporating a device like the above mentioned two successful units (miniaturized devices with low power, mass, and volume requirements) will provide data during ambient radiation and enhanced radiation times of the proposed telescope operation. It is known that the data collected by the space telescope will be influenced by the disturbances radiation caused disturbances. Also, it is well known that the electronics will have irreparable damages from the enhanced radiation events in space for any telescope operation related and data collection electronics over a long period of time and hence the radiation measuring assessment devices are essential.

3. Cucinotta and Saganti, Encyclopedia of Lunar Science (2019)
4. Cucinotta, Kim, and Saganti, Nuclear Instruments and Methods ... (2019)
5. Cucinotta, Cacao, Kim, and Saganti, Radiation Protection Dosimetry (2018)
6. Saganti, Cucinotta, …, Space Science Reviews (2004)
Galactic Bulge Time Domain Survey solar system astronomy, exoplanets and exoplanet formation, stellar physics and stellar types, stellar populations and the interstellar medium, galaxies, the intergalactic medium and the circumgalactic medium, supermassive black holes and active galaxies, large scale structure of the universe Space Radiation, Galactic Cosmic Rays, Solar Particle Events, Coronal Mass Ejection, Neutron Production
Rachel Street Las Cumbres Observatory Y. Tsapras, Heidelberg University; E. Bachelet, Caltech/IPAC; J. Sobeck, CFHT; P.M.McGehee, SLAC; M. Dall'Ora, INAF-OACN; M. Hundertmark, Heidelberg University;M.Di Criscienzo, INAF-OAR; M. Makler, ICAS-UNSAM & CBPF, M. Rabus, Universidad Católica de la Santísima Concepción, K. Dage, McGill University, W. Clarkson (University of Michigan-Dearborn); S. Khakpash, Rutgers University, Benjamin Montet, University of New South Wales, N. S. Abrams, UC Berkeley Optimizing the science return from simultaneous NIR and Optical Timeseries photometry in the Galactic Bulge Over the next decade, the overlap of two groundbreaking surveys offers us a chance to characterize time-variable phenomena in the Galactic Bulge to an unprecedented degree.

The Nancy Grace Roman Space Telescope will deliver exquisitely high precision NIR timeseries photometry and astrometry of millions of stars in the Galactic Bulge once it launches in ~2026. The Vera C. Rubin Observatory will provide contemporaneous timeseries photometry in optical passbands, after its commissioning in late 2024.

The combined data from these two great observatories will cover key passbands in the Spectral Energy Distributions of most stars, allowing us to measure the properties of stars in the Roman Galactic Exoplanet Survey (RGES). But complementary time-domain coverage of these objects will enable the characterization of a wide range of stellar variability, such as Cepheids and RR Lyrae that will help us to trace galactic structure to greater distances thanks to these survey's fainter limiting magnitudes. It can also help to measure the parameters of exoplanet transits detected by Roman, and to rule out blending by stellar binaries in these crowded regions.

By coordinating the survey strategies of both Roman and Rubin, we can enhance the scientific return of the RGES. Roman's coverage of the Galactic Bulge will necessarily suffer gaps of several months between survey periods. Rubin observations during these periods will help to constrain the morphology of microlensing lightcurves after Roman stops observations, which is particularly important for verifying the microlensing parallax, and could allow us to detect additional anomalous features. For this reason, we propose further exploration of the scientific benefits of inter-season gap coverage as well as near-simultaneous observations by Rubin of the RGES fields. By understanding what observations can be delivered within the constraints of both major surveys, the community will also be able to explore how co-survey observations from other ground-based facilities, such as the PRIME telescope and DECam on the Blanco 4m, can enhance the overall science return.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation, stellar physics and stellar types, stellar populations and the interstellar medium microlensing detection of exoplanets, survey strategy optimization, stellar variability
Radek Poleski Astronomical Observatory, University of Warsaw Makiko Ban (Astronomical Observatory, University of Warsaw), Jan Skowron (Astronomical Observatory, University of Warsaw) Search for exomoons There are more than 5,000 exoplanets currently known, but there is no confirmed exomoon. The detection of exomoons will significantly further our understanding of formation and evolution of planetary systems and open a new path for search for extraterrestrial life. This new path comes from the fact that moons of giant planets can be significantly heat up by tides from the host planet. Additionally, a large number of moons of giant planets result in a large diversity of surface and atmospheric compositions, moon sizes etc., which provide diverse conditions for life to develop. We observe the signs of both moon heating and large moon diversity in the Solar System.

Thus, we propose to use the Roman Galactic Exoplanet Survey (RGES) to search for microlensing exomoons. The existing simulations of microlensing planet detection for RGES indicate that this survey should be sensitive to star-planet systems with planet mass down to around mass of Ganymede (thanks to high-cadence continuous observations of a large number of faint bulge stars). For triple-lens systems (star-planet-moon in this case) the detection of the lowest-mass component is easier than in the case of binary lens with only the highest- and lowest-mass components (star with planet that of a moon in this case). Hence, RGES is going to be sensitive to exomoons. Even if no exomoons are detected, it will be possible to place interesting upper limits on the number of such objects. The search will benefit from increasing cadence of Roman observations (could be applied to part of the footprint) and concurrent observations from the Euclid satellite.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation Natural satellites, Exoplanets, Extrasolar gas giants
Radek Poleski Astronomical Observatory, University of Warsaw Bulge Initial Mass Function Our understanding of the mass function of low-mass stars is limited to the Solar neigbourhood. This limitation further restricts our knowledge of the Initial Mass Function (IMF) or dark matter content in the Galactic bulge. The low-mass stars are observed in the Galactic bulge (most importantly by the Hubble Space Telescope) but we cannot translate observed luminosity function into a mass function because we do not have proper statistics of stellar binary systems. The low-mass stellar binaries located a few kpc away cannot be spatially resolved, nor can they be found using radial velocity shifts. The Roman Galactic Exoplanet Survey (RGES) has potential to significantly increase our understanding of binarity statistics in the disk and in the bulge, which then can be used to calculate the IMF as a function of galactocentric distance or the dark matter content in the Galactic bulge. First, the RGES will provide catalogs of stars that will include even the lowest-mass stars in the bulge. Second and more importantly, the RGES will provide thousands of microlensing events with stellar binaries as either lenses or sources. For each of these events we will be able to measure projected separations and either a mass ratio (binary lens events) or a flux ratio (binary source events). Thanks to higher-order microlensing effects (microlensing parallax, finite source effect, astrometric shift, or detection of the lens flux), we will measure distances to the lenses. All these quantitites allow constraining the binarity statistics with accuracy not possible currently with ground-based microlensing searches and the Hubble Space Telescope luminosity function. Galactic Bulge Time Domain Survey stellar physics and stellar types, stellar populations and the interstellar medium Binary stars / Trinary stars, Low mass stars, Gravitational microlensing, Galaxy bulges, Galaxy disks
Robert Wilson NASA Goddard Space Flight Center Thomas Barclay Demographics of Transiting Exoplanets in the Galactic Bulge Time-Domain Survey The occurrence of planets (particularly close-in planets and giant planets) has repeatedly been shown to be correlated with stellar metallicity. However, due to the chemical and kinematic evolution of the Milky Way, interpreting this correlation in the context of planet formation and evolution is extremely difficult because stellar metallicity in the Solar neighborhood is highly correlated with properties such as age and alpha abundance. Due to these correlations, disentangling the role of age and composition in exoplanet demographics requires a targeted search across stellar populations with distinct age and metallicity distributions not accessible with current transiting planet surveys. For giant planets in particular, occurrence rates in differing Galactic environments (such as the Bulge and inner regions of the thin disk), will illuminate the relative importance of tidal decay (which predicts a higher planet occurrence for younger stars) and enhanced core accretion (which predicts a higher planet occurrence for metal-rich stars), while occurrence rates in the thick disk will shed light on core accretion and the role of Alpha elements such as Si, Mg, and C, which are thought to play an important role in planetesimal formation.

The Roman Galactic Bulge Time Domain Survey (GBTDS) is capable of performing such a targeted search, and should therefore place unprecedented constraints on the relative roles of stellar metallicity, alpha abundances, and age on exoplanet demographics. In addition to the 1000s of microlensing exoplanets on wide (~1-10 au) orbits, the GBTDS will have the cadence and photometric precision necessary to discover ~100,000 exoplanets on close-in (<0.3 au) orbits by the transit technique, with some having distances as far as ~12-16 kpc, representing an unprecedented yield across Galactic environments such as the thin disk, thick disk, and bulge.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation, stellar populations and the interstellar medium Transits, Exoplanet evolution, Exoplanet formation, Stellar Populations
Sam Grunblatt Johns Hopkins University Constraining Star and Planet Formation and Evolution with Post-Main Sequence Transiting Planetary Systems in the Galactic Bulge The Galactic Bulge Time Domain Survey will allow for the detection of a new population of exoplanets via the microlensing and transit methods. 15-minute cadence observations that reach a precision of 1 ppt in a single observation of a 15th magnitude star in a 1.0-2.0 micron bandpass over a 72-day long baseline will also allow the characterization of stellar oscillations in post-main sequence stars, allowing stellar masses and ages to be measured to precisions not achievable for other populations. For low-luminosity red giant stars (~2.5-8 Rsun), both transiting exoplanets and stellar oscillations will be detectable.

Following previously published estimates of transiting planet yield from Roman and assuming the observing strategy described above, we expect roughly 10,000 transiting exoplanets to be detected orbiting low-luminosity red giant stars in the Galactic Bulge Time Domain Survey, increasing the population of planets known transiting evolved stars by at least two orders of magnitude. This exoplanet sample will span a larger volume than any previous transiting exoplanet survey, and will allow for homogeneously determined, precise stellar masses (with <10% uncertainty) and ages (with <20% uncertainty) from asteroseismology. The metallicity gradient and wide range of stellar masses present within the Galactic bulge, combined with precise stellar ages, will provide a more complete picture of planet occurrence trends with fundamental stellar properties than previously possible, and will resolve mysteries such as the role of planet inflation and migration in planet evolution. In addition, the well-characterized stellar parameters will assist with galactic archaeology efforts, as well as inform stellar models, improving currently inaccurate models of post-main-sequence evolution near the base of the red giant branch. We propose to use light curves of low-luminosity red giant stars produced by the Galactic Bulge Time Domain Survey to expand our understanding of star and exoplanet populations.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation Exoplanet evolution, Transits, Stellar evolution
Scott Gaudi The Ohio State University David Bennett The Roman Galactic Exoplanet Survey The Roman Galactic Bulge Time Domain Survey (RGBTDS) is one of the three core community surveys that will be carried out by the Roman Space Telescope during its prime mission. While the exact survey parameters remain to be determined, it will notionally consist of repeated high-cadence (~15 minute) observations primarily in one broad (1-2 μm) filter of a few square degrees toward the central Galactic bulge during roughly six of the 72-day seasons when the bulge is visible from Roman spread out over the five-year prime mission, for a total survey duration of ~430 days. The recommendation of the RGBTDS by the Astro2010 decadal survey was based upon the unique cold exoplanet demographics science that will be produced by the Roman Galactic Exoplanet Survey (RGES), using the gravitational microlensing technique. The wide orbit exoplanet demographics results from RGES will provide a unique window on the properties of exoplanetary systems that is needed to understand the formation and evolution of planetary systems. It cannot be duplicated by any other proposed exoplanet detection method or any ground-based microlensing survey. Tens of thousands of microlensing events are expected to be detected during the RGBTDS. These events will be sensitive to cold exoplanets orbiting the microlens host stars. The RGES survey will be sensitive to all planets with mass greater than the Earth and semimajor axis greater than 1 AU, including free-floating planets, thereby completing the statistical census of exoplanets begun by Kepler. It is expected to detect thousands of planets with mass down to that of roughly the moon. With this large sample, RGES will (1) measure the mass function of cold bound exoplanets with masses in the range 1 M_Earth < m < 30 M_Jupiter and orbital semi-major axes ≥ 1 AU to better than 15% per decade in mass, (2) measure the frequency of bound Mars-mass embryos in the range 0.1 M_Earth < m < 0.3 M_Earth to better than 25%, (3) determine the masses of, and distances to, host stars of > 40% of the detected planets with a precision of 20% or better, and (4) measure the frequency of free-floating M_Earth-mass planets to better than 25%, assuming one such planet per star in the Galaxy, and estimate ηEarth to a precision of 0.2 dex via extrapolation from larger and longer-period planets. The RGES survey will also be sensitive to satellites of bound and free-floating planets with mass greater than roughly the moon, circumbinary planets, multiple-planet systems, analogs of all of the solar system planets except for Mercury, planets orbiting brown dwarfs, white dwarfs, neutron stars, and black holes, and planets orbiting stars all along the line of sight from the sun to the Galactic center.

In addition to the dramatic increase in the exoplanet yield and parameter space over which RGES will probe exoplanet demographics as compared to ground-based surveys, it will also be possible to routinely measure host star masses and distances, and thus planet masses and physical separations, for a significant fraction of all the detected systems using Roman data alone. This is in contrast to ground-based microlensing planet surveys, where such information is only possible for a subset of the detected systems, and then only with resource-intensive follow-up or auxiliary observations. Routine mass measurements with the RGES data are made possible by the high angular resolution and exquisite photometric and astrometric precision enabled by the relatively quiet, stable, space-based, platform of Roman at L2. While the requirements for the exoplanet yield as a function of mass largely fixes the cadence, total duration, and area of the survey, the ability to measure host and planet masses is also strongly affected by the length of the RGBTDS seasons and which of 10 bulge seasons within the five-year primary survey are chosen for observations. Longer and more widely-spaced observing seasons generally improve the number and precision of the mass measurements. It may be necessary for RGES to use the first two and last two RGBTDS observing seasons in order to meet its exoplanet mass measurement requirements.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation Exoplanet formation, Exoplanet detection methods, Galactic center, Natural satellites (Extrasolar), Free floating planets
Sean Terry University of California - Berkeley Jessica Lu, Andrea Ghez, Matthew Hosek Jr., Casey Lam, Natasha Abrams Transients at the Galactic Center with Roman While the Roman Galactic Bulge Time Domain Survey (GBTDS) will monitor millions of stars toward the center of the galaxy, it will ostensibly avoid the lowest latitude region covering the galactic center's (GC) supermassive black hole (Sgr A*) and surrounding stellar population. Given the GC is in the immediate vicinity of the provisional GBTDS (0.5 < b < 2 degrees away), the opportunity to observe this area is compelling and can significantly bolster the scientific return of the GBTDS. This pitch focuses on transient phenomena (both microlensing and non-microlensing) that Roman can study in a 0.28deg2 region centered on the GC. Details on additional GC science cases can be found in an adjacent Roman pitch (M. Hosek Jr).

Along with microlensing, these observations would also search for possible lensing from Sgr A* itself, as well as enabling studies of phenomena associated with young populations like x-ray binary (XRB) outbursts and young stellar flares. Near-IR counterpart observations of XRB outbursts with Roman can probe the mass accretion rate and its variability between outbursts for these dynamical systems, which is currently not well understood, particularly in the crowded GC region. A large Roman footprint on the GC would also deliver high precision photometry and astrometry of three of the most massive young star clusters in the milky way (Arches, Quintuplet, Nuclear Star Cluster). This will allow for dynamical studies of the clusters and their interaction with the central potential, the clusters and surrounding star formation rate, and more. Finally, the effect of higher extinction within the GC will be balanced by an overall higher incidence of transient phenomena along this sight-line. The Ks-band extinction surrounding SgrA* varies between 1.4 < AKs < 3.5 (Gonzalez et al. 2012), thus the Roman GC strategy will address this by observing in the reddest possible filter(s) (F213, central wavelength = 2.12um).
Galactic Bulge Time Domain Survey stellar physics and stellar types, stellar populations and the interstellar medium, supermassive black holes and active galaxies galactic center, stellar populations, gravitational lensing, star clusters
Shota Miyazaki JAXA/ISAS Daisuke Suzuki (Osaka U.), Takahiro Sumi (Osaka U.), Naoki Koshimoto (NASA/GSFC) Survey for Exoplanets and Brown Dwarfs in the Galactic Center via Microlensing Xallarap Effect Miyazaki et al. (2021) found that the microlensing events observed by the Galactic Bulge Time Domain Survey (GBTDS) will also contain valuable information about close-in companions (including exoplanets) around source stars in the Galactic bulge, which can be explored by the microlensing xallarap effect. This science outcome does not require any additional observations than the the GBTDS. However, Miyazaki et al. mentioned that observations with multiple passbands can help to distinguish the xallarap signals from other phenomena and to characterize the properties of source stars. Therefore, it could be useful to increase observation cadence with other passband than the survey passband during the GBTDS. Galactic Bulge Time Domain Survey exoplanets and exoplanet formation, stellar physics and stellar types Gravitational microlensing, Exoplanet detection methods, Galactic center
Susmita Das Konkoly Observatory, CSFK, Budapest László Molnár Discovering new BLAPs in the Galactic plane Blue large-amplitude pulsators (BLAPs) represent a new class of extremely rare and hot pulsating stars with unusually large amplitudes and short periods (in the range of 20-40 min). These stars exhibit sawtooth light curves, similar to those of RR Lyraes and classical Cepheids. The evolutionary status of these stars remains unknown; however, pulsation theory predicts that they may be evolved low-mass stars with inflated helium-enriched envelopes.

Ever since the discovery of the first 14 BLAPs from the OGLE-IV survey, these rare stars have also been discovered by other surveys like Gaia DR2 and ZTF DR3. Their rare occurrence is thought to be because of their evolutionary history within interacting binary systems and their short timescales over which they transition the instability strip. All the BLAPs currently known are located in the Galactic plane with magnitudes in the range 15-19 mag. In addition to being rare, certain observational limitations may hinder their detection. BLAPs have intrinsically blue colors and the interstellar dust in the Galactic plane may prevent these sources from being easily identified. Roman could thus prove instrumental in discovering many additional new BLAPs and in unlocking their origin with its high sensitivity, high cadence and precise photometry, especially within the Galactic plane.
Galactic Bulge Time Domain Survey stellar physics and stellar types Variable stars, Stellar evolution
Szilard Kalman MTA-ELTE Exoplanet Research Group Dr. Gyula Szabo M. Galactic Bulge Time Domain Survey - Exoplanet Phase Curves The study of exoplanetary phase curves is one of the fundamental ways of understanding planetary atmospheres, interiors and ultimately planet formation itself. Detection of the thermal emission of the planet is more conveniently done in infrared (IR) wavelength ranges, as was proven by the Spitzer Space Telescope. The high-precision, wide-band, 15-minute cadence observational strategy, available for the Galactic Bulge Time Domain Survey, will be the first survey-type mission, where the IR study of transiting exoplanets will be feasible (Galactic Bulge Time Domain Survey - Exoplanet Phase Curves -- GBTDS-EPC).

By carrying out GBTDS-EPC, we can expect to get improved parameters of already known transiting exoplanets, as well as the discovery of many new short-period planets, where the phase curve effects will be detectable. GBTDS-EPC would also enable the discovery of exoplanets orbiting stars that are a lot fainter than what is currently feasible by the data available from the optical surveys of Kepler and the Transiting Exoplanet Survey Satellite. This is especially interesting for red dwarfs, where exoplanets that are inside the so-called habitable zone could be studied with an exceptional S/N during each of the 72 days long seasons by GBTDS-EPC.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation Phase curves, atmoshperes, thermal emission, transting exoplanets
Szilard Kalman MTA-ELTE Exoplanet Research Group Dr. Gyula Szabo M. A quest for exomoons with the Roman Space Telescope Despite the thousands of known exoplanets, and the numerous moons known from our Solar System, there is no unambiguous observation of a moon-like companion to an exoplanet (called 'exomoon'). Not all planets are good gandidates for such a search for exomoons, because moons around close-in exoplanets are likely dynamically unstable on the time scale of 100 - 1000 Myr. Due to its small size, the detection of a transiting exomoon is an extremely challenging task, which is even theoretically only feasible from ultraprecise space-based photometry. Infrared wavelengths offer a higher chance for detection, because of the lower jitter and more importantly, due to the thermal contribution of tidally heated/overheated/spotted moons, making the Roman Space Telescope a prime instrument for the first secure exomoon detection.

The Galactic Bulge Domain Survey of the Roman Space Telescope, with its 15 min wide-filter cadence, has the potential of providing exceptionally high precision data even for relatively faint targets, whose observations otherwise might only be feasible with the James Webb Space Telescope. Because of the differences in the observing strategy between the two observatories, the quest to find the first unassailable exomoon would greatly benefit from observations carried out throughout the Galactic Bulge Domain Survey.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation Exoplanets, Natural satellites (Extrasolar), Planet hosting stars
Takahiro Sumi Osaka University D. Suzuki, N. Koshimoto, S. Miyazaki Mass measurement of FFP with source color measurements We can measure the lens mass from the angular Einstein radius θ_E in combination with the (space) microlensing parallax. The θ_E measurement alone is still useful for constraining the mass of the lens objects even without the microlensing parallax. The of θ_E be estimated from the finite source size effect parameter ρ=θ_*/θ_E from the light curve. Here the source color is needed to estimate the source angular radius θ_* to derive θ_E. A typical timescale of magnification by a terrestrial mass Free-floating planet (FFP) is a few hours. Therefore, it is important to increase the observational cadence with other passbands in the Galactic Bulge Time Domain survey as possible. The color information during the magnification is also useful for discriminating the real microlensing event due to FFP from flare stars which are the major contaminants in the very short timescale events. Galactic Bulge Time Domain Survey exoplanets and exoplanet formation Exoplanets, Free floating planets, Exoplanet detection methods
Takahiro Sumi Osaka University D. Suzuki, N. Koshimoto, S. Miyazaki Search for quasars behind the Galactic bulge via variability The quasars have been found by their long term irregular variability behind the LMC. We propose to apply the same quasar survey toward the Galactic Bulge. Such quasars can be used as the astrometric reference for the precise measurements of absolute proper motions of stars and the Galactic center. A deep accurate long term light curves from Roman Galactic Time Domain Survey can provide good candidates for quasars behind the Galactic bulge from their variability. The selected candidates will be confirmed by follow-up spectroscopic observation by the ground base large telescopes, like Subaru, Keck and VLT. The occasional observations filling the gap of the main Galactic Bulge Time Domain Survey may increase the success rate for finding the quasars. Galactic Bulge Time Domain Survey supermassive black holes and active galaxies Quasars, Astrometry, Galactic center,Galaxy bulges
Thomas Barclay UMBC Robert F. Wilson Stellar characterization in the Galactic Bulge Fields Roman observations of the Galactic Bulge provide unprecedented access to this region of the Galaxy. In addition to enabling exoplanet microlensing, these data will support numerous science investigations including the study of transiting exoplanet, asteroseismology, stellar flares, and eclipsing binaries. However, these investigations all rely to varying degrees on being able to determine the properties of the stars in the bulge fields. With 10's of millions of stars, and high stellar density, this is not a trivial problem as the bulge fields are not amenable to Gaia observations. Fortunately, the Roman Wide Field Instrument provides the capabilities to greatly enhance stellar characterization through the use of the the filters. By collecting images using all 8 Roman filters we could determine accurate stellar properties of all the stars in the bulge fields. These images need not be collected regularly; a few times per observing season would be sufficient. A minimal investment in observing resources would provide a large enhancement in science return. Galactic Bulge Time Domain Survey exoplanets and exoplanet formation, stellar physics and stellar types, stellar populations and the interstellar medium Planet hosting stars, Exoplanets, Binary stars / Trinary stars, Stellar distance, Evolved stars
Thomas Kupfer Texas Tech University on behalf of LISA multimessenger and pre-EM working A minute cadence Roman survey to identify strong gravitational wave sources Compact binaries are a class of binary systems with orbital periods below a few hours, consisting of a black hole, neutron star or white dwarf primary and a helium star, white dwarf or neutron star secondary. These systems are predicted to be the dominant gravitational wave sources detectable by the Laser Interferometer Space Antenna (LISA), an approved ESA/NASA mission on track for mission adoption in November. At least several hundred, maybe even over a thousand of those binaries are predicted to be sufficiently bright in electromagnetic wavebands to allow detection in both the electromagnetic (EM) and the gravitational (GW) bands, providing a unique opportunity to perform multi-messenger studies on a statistically significant sample. This makes these binaries ideal multi-messenger sources where EM and GW can complement each other and, in some cases, are even required to break degeneracies. The GW signal alone has a strong degeneracy between its amplitude and the system's inclination angle as well as in some cases a poor sky localization of several square degrees. This degeneracy can be solved with prior information on the period, sky localization, mass, distance, and inclination from EM measurements. Thus multi-messenger observations of these sources have the potential to yield more robust masses, radii, orbital separations, and inclination angles than can be achieved using either GW or EM observations alone. However, the improvement in system properties from multi-messenger studies depends strongly on the signal-to-noise in the LISA data as well as on the precision of the derived EM parameters and their correlations.

Currently, we know only about two dozen of these sources. Their light curves show variations on timescales of the orbital period, e.g., due to eclipses or tidal deformation of the components. Therefore, photometric time-domain surveys are well suited to identify LISA binaries in a homogeneous way. Binary population studies have shown that a large number of these sources are expected to reside in the Galactic Bulge region, ideally located for the Galactic Bulge community survey. The Roman telescope combines unprecedented sky resolution with large photometric depths unreachable from the ground. We propose to use these unique capabilities as part of the Galactic Bulge community survey to conduct a several hours continuous cadence survey mainly targeted to discover rapid variability coming from compact gravitational wave sources which are ideal for multi-messenger studies. This dataset will also provide a unique resource to search for electromagnetic counterparts of binaries discovered by LISA. The Roman telescope is the ideal resource to perform such a survey. The sky resolution is at least an order of magnitude better than the seeing-limited ground-based observations, leading to significantly less blending. A 60 sec exposure on Roman will reach a limiting magnitude of 25, providing a large expected sample of compact LISA binaries between Earth and the Galactic bulge.. Continuous cadence is key to rapid events or events with short duty cycles. Eclipsing LISA binaries with orbital periods less than a few hours have duty cycles of less than 10% i.e., eclipse durations can be as short as one minute up to a few minutes. Therefore, a 15 min cadence is not ideal to detect the short period variability of these binaries. We request to use the Wide Field Instrument with the F062 or F087 filter. As an alternative we could also alternate between the F062 and the F087 filters which would provide additional color information. The F062 or F087 filter is the ideal compromise to be sensitive to the hotter white dwarfs and extinction towards the Galactic Bulge region. Based on a study by Digman et al. 2023 and other binary population studies, we expect to find several 10s of LISA binaries. Additionally we expect to find 1000s of other sources with rapid variability such as flaring stars, compact pulsators, and rapid rotators. The regular 15 min cadence survey is expected to discover many planets including potentially planets around compact binaries. Our survey will ideally complement the regular 15 min and characterize planet hosts on short minute timescales, e.g. binarity, flaring. We would like to emphasize that continuous cadence observations will provide a unique observing mode for the Roman telescope opening a new window to study rapid variability in dense Galactic Bulge regions with space-based quality.
Galactic Bulge Time Domain Survey exoplanets and exoplanet formation, stellar physics and stellar types, stellar populations and the interstellar medium White dwarf stars, Binary stars / Trinary stars, Stellar evolution, Variable stars, Planet hosting stars
Tsuyoshi Terai Subaru Telescope, National Astronomical Observatory of Japan Fumi Yoshida Rotational Light Curves and Phase Curves of Small Solar System Bodies Galactic Bulge time-domain survey will allow us to acquire a large number of samples of short- and long-term light curves of small solar system bodies such as near-earth objects, main-belt asteroids, and trans-Neptunian objects. The former ones provide the distribution of rotation periods which is useful for investigating the inner structure of tiny asteroids, and also give new knowledge regarding the binary rate of TNOs as well as the shape distribution of a variety of small-body populations. The latter ones include brightness variation against solar phase angle (i.e., Sun-object-observer angle) which is called a phase curve. The slope/shape of the phase curve are known to be dependent on surface properties such as reflectivity and surface roughness so that we can get meaningful information about asteroid surfaces from such data. Because the survey field is located close to the ecliptic plane, we will be able to collect photometric monitoring data of a large number of very faint small bodies through a long period of time. Galactic Bulge Time Domain Survey solar system astronomy small solar system bodies, light curve, phase curve, inner structure, surface properties
Veselin Kostov NASA/SETI Roman's Royal Road to Stellar Astrophysics Eclipsing binary stars are one of the foundations upon which stellar astrophysics is built. They serve as calibrators for stellar sizes, masses, temperatures, and luminosities, which benefits nearly every topic in astronomy. Eclipsing binaries (EBs) are ideal laboratories to study stellar structure, formation and evolution in dynamically complex environments where multiple stars can interact with each other at multiple evolutionary stages through mass transfer, tidal effects, mergers, etc. Studies of EBs have shown that about 10-20% of them are members of stellar multiples, led to the discovery of a few dozen compact triple and quadruple systems, two sextuple systems, and a handful of transiting circumbinary planets. Despite the ubiquitous distribution of binary stars throughout the local neighborhood and more than two centuries of study, pressing questions remain unanswered. For example, it is unclear whether the multiplicity properties are universal or depend on the formation history, environment and/or stellar mass, why close binary stars tend towards equal masses, what is the origin of the brown dwarf desert, and even how stellar multiplicity affects planet formation.

Addressing these questions depends upon, first and foremost, detecting and characterizing a large number of EBs in a variety of Galactic environments. It also requires a systematic comparison of (i) the physical and orbital properties of EBs in the local neighborhood to EBs in the Galactic bulge and in globular clusters; (ii) the occurrence rates of nearby triple and higher order systems to their counterparts in denser environments; and (iii) the EB populations in the Milky Way to those in nearby galaxies. This has not been possible until now due to various observational biases associated with previous surveys: weather, season, resolution, precision, sensitivity, dwell time, etc. The Roman Space Telescope has the unique opportunity to provide high-precision photometry of hundreds of thousands of EBs covering a wide range of physical parameter space and environments in the Galactic bulge, globular clusters, and even nearby galaxies. This treasure throve of data will dramatically improve our understanding of stellar formation, evolution and multiplicity.
Galactic Bulge Time Domain Survey stellar physics and stellar types Astronomical models, Binary stars / Trinary stars, Stellar evolution,
William A. Dawson Lawrence Livermore National Laboratory Jessica Lu, Natasha Abrams, Simeon Bird, Josh Bloom, George Chapline, Nathan Golovich, Hannah Gulick, Ming-Feng Ho, Casey Lam, Peter McGill, Scott Perkins, Kerianne Pruett, Sean Terry, Keming Zhang A Massive Compact Object Census There is potential for the Galactic Bulge Time Domain Time Domain Survey Core Community Survey to enable a statistical census of massive compact objects (stars, white dwarfs, neutron stars, stellar-end-product black holes, and primordial black holes) in both isolated and binary configurations. This survey data has the potential to enable the detection of such systems via multiple astrometric and photometric techniques including gravitational microlensing, astrometric wobble, and periodic photometric variability from transits or tidal distortions. Roman is unique in its ability to simultaneously enable all of these detection methods. Ultimately, such a census will advance our understanding of stellar death and the initial-final mass relation, compact object population properties, the existence of primordial black holes, and the frequency of mergers that produce gravitational wave sources. Thus, extending the survey design considerations to include the high mass-end of compact object could greatly extend the Galactic Bulge Time Domain Survey's (GBTDS) core science mission of performing "a statistical census of exoplanets from outer habitable zone to free floating planets via the microlensing technique." Galactic Bulge Time Domain Survey stellar physics and stellar types, stellar populations and the interstellar medium, large scale structure of the universe stars, white dwarfs, neutron stars, stellar-end-product black holes, primordial black holes
Abram Jackson Citizen Using Coronagraphy to Image Other Astronomical Bodies in Search of Dark Matter Ever since Galileo, humans have pointed their telescopes at bright things. Even with our latest and best infrared and radio telescopes, we tend to point them at what is "brightest." This is natural, but it is also potentially very limited. Most of the mass in the universe is unaccounted for. As Neil deGrasse Tyson has said, "Everybody you know and love and heard of and think about and see in the night sky through a telescope: four percent of the universe." It is possible that dark matter does not produce any photons whatsoever, but we cannot rule out that at least some dark matter is simply overwhelmed by nearby bright things. We should use the advanced coronagraph instrument on the Roman to look at the area around all objects under observation through the Core Community Surveys, such as supernovae, in order to potentially identify dark matter that is very dim. In theory, these could be red dwarfs, primordial black holes, or even possibly yet-to-be-identified astronomical bodies. We cannot know what we will find when we look at things that are dim instead of those that are bright, but now is our best opportunity to find out. High Latitude Time Domain Survey the intergalactic medium and the circumgalactic medium, large scale structure of the universe dark matter distribution, dark energy, galaxy dark matter halos, supernovae
Anowar Shajib University of Chicago Strong lensing time delays from HLTDS: a complete Roman-only dataset to measure the Hubble constant by combining lensed and non-lensed supernovae Roman's HLTDS will discover ~10 strongly lensed type Ia supernovae (SNIae; Pierel et al. 2021). The HLTDS can measure the time delays between the lensed SN images from the color curves. These time delays will measure the Hubble constant and other cosmological parameters (review by Suyu et al. 2023). High-resolution Roman imaging will suffice for detailed lens modeling. Additionally, we can estimate the lens magnification of the lensed SNIa by comparing it with the Roman sample of non-lensed SNIa. This magnification breaks the mass-sheet degeneracy (Birrer, Dhawan & Shajib 2022). Thus, stellar velocity dispersion will not be necessary to constrain the mass-model uncertainty. The spectroscopic component will measure the redshifts of the lens galaxy and the SN. Photometry and spectroscopy of the line-of-sight galaxies will constrain their lensing perturbations. Thus, Roman's HLTDS dataset will be complete for time-delay cosmography. Yet, microlensing can induce a systematic if time delays are measured from the light curves. The initial rising phase of the SN light curve is achromatic for microlensing. Thus, early detection of an SN is crucial to pinpoint the time delays in this achromatic phase (Goldstein et al. 2018). High Latitude Time Domain Survey large scale structure of the universe Cosmological parameters, Cosmology, Dark energy
Ariel Goobar Stockholm University Nikki Arendse, Ana Sagues Carracedo Strongly Lensed Supernovae The depth, cadence and spatial resolution of the high-z SNIa program with the Nancy Grace Roman Space Telescope will enable the discovery and accurate study of several tens of strongly lensed supernovae, about ⅓ SNe Ia. A population of these rare and precious events can both shed light on cosmological parameters, as well as probe the stellar composition and possible substructures of the cores in the deflecting galaxies. There is also a unique window to study the ISM of distant galaxies: Thanks to the wide wavelength coverage, detailed information about dust properties can be inferred through mapping of the differential extinction along the lines of sight of multiple supernova images.

Besides measuring lensed supernova time delays, Roman's spectrograph will also provide redshifts of the lensed sources, which will significantly help with classifications. Observations from Roman will complement lensed supernova discoveries from the Vera Rubin Observatory by providing redshifts and longer wavelength coverage. Additionally, Roman will discover a population of high-redshift and small angular separation lensed supernovae that will be out of reach for the Rubin Observatory.
High Latitude Time Domain Survey stellar populations and the interstellar medium, galaxies, large scale structure of the universe Gravitational lensing, Cosmology, Supernovae, Dark matter distribution, Interstellar dust
Daniel A. Yahalomi Columbia University Ruth Angus, David N. Spergel, Daniel Foreman-Mackey Detecting Solar System Analogs through Joint Radial Velocity/Astrometric Surveys If it is properly tested during the calibration stage of the mission, Roman will be capable of precision astrometry. As presented in WFIRST Astrometry Working Group et al. 2019, an astrometrically calibrated Roman Telescope will be capable of at least a factor of three improvement over the current state of the art astrometric observations in this wavelength range. Specifically, Roman should be properly calibrated to astrometrically observe bright nearby stars, where combining with existing datasets (ie Gaia) will allow for a baseline of several decades. For these bright nearby stars, there are two possible methods to observe without saturation: (1) diffraction spike method and (2) spatial scanning. In the diffraction spike method, observations are centered on the detector's diffraction spike, where we could utilize Roman's H4RG detectors for which pixels don't bleed into nearby pixels. In spatial scanning, the telescope is slowly slewed creating spatial tracks for the brighter stars, allowing for the observation of reference stars in the same field and spreading the signal over hundreds, or even thousands, of pixels to avoid saturation. Subsequent spatial scans in two perpendicular directions allows for three-dimensional high precision observations. For both methods, measurement accuracy will likely be limited by systematics, and so it is ideal to take multiple observations of a system to reduce uncertainties (WFIRST Astrometry Working Group et al. 2019). While we need to further study the exact Roman filter(s) best suited for precision astrometry of bright nearby stars, Sowmya et al. 2021 showed that astrometric photocenter displacements in the Small-JASMINE (1,100-1,700nm) infrared filter are smaller than those in the Gaia-G filter and Kaplan-Lipkin et al. 2022 showed that observing astrometrically in multiple band passes can reduce correlated noise and improve detectable planet masses at 1 au by up to a factor of 10. Additionally, there is an added benefit for Roman astrometry in infrared wavelengths, as Roman more fully samples the PSF in the infrared than in the optical. Therefore, we suggest that Roman astrometry be conducted with multiple filter observations per epoch and with filters towards the infrared end of Roman's observing capabilities.

We propose an observing program targeting ~40 bright nearby G and K dwarfs observed by the Terra Hunting Experiment (THE: with the HARPS3 spectrograph. Hall et al. 2018 showed that the baseline program, ~1,800 observations of these 40 targets over 10 years, should be capable of detecting the radial velocity (RV) signal of an Earth-like planet in mass and temperature. Subsequently, Yahalomi et al. 2023 investigated the yield of a joint radial velocity and astrometric survey combining these RVs with Gaia and Roman astrometry. We showed that the combined observations should be sufficient to detect and characterize Solar System-analogous planetary architectures that contain both an Earth-mass planet in the habitable zone and a cool gas giant (CGG). Systems with both an Earth-like exoplanet and a CGG-like exoplanet are of particular interest as the formation and migration of CGGs and the interactions between gas giants in our Solar System played a critical role in the characteristics of the planets in our Solar System. With 10 years of Roman observations, a cadence of ~4 observations per year, and an assumed Roman 1σ measurement error of 5 micro-arcseconds, Yahalomi et al. 2023 showed that Roman astrometry improves the detection precision for CGG masses by a factor up to ~6 and periods by a factor up to ~5 over a survey with only THE RVs and Gaia astrometry. Obtaining precise orbital periods for potential CGGs outside Earth analogs will be essential in studying the near mean motion resonance effect found for multi-planet systems in closer-in orbits (Petrovich et al. 2013). Therefore, the addition of several well timed Roman observations per year throughout its lifetime, which could allow for 1% detections of CGG periods out to Saturn-like orbits, would be crucial to understanding the orbits of exoplanetary systems that resemble our Solar System. Further, the ~25 year baseline made possible by combining Gaia and Roman astrometry will likely be especially important for resolving the orbit of three planet systems (Earth-Jupiter-Saturn).
High Latitude Time Domain Survey exoplanets and exoplanet formation Astrometry, Exoplanet detection methods, Exoplanet systems, Exoplanets
Greg Aldering Lawrence Berkeley National Lab Saul Perlmutter Balanced Prism Plus Filter Cadence in the High Latitude Time Domain Survey Among the baseline concepts for the "high latitude time domain survey" (HLTDS) as outlined in Rose et al (2022, arXiv:2111.03081), there is an advantage to choosing the observing strategy that gives comparable time to prism and filter observations. Such a balanced prism-plus-filter strategy makes it possible to measure the expansion history of the universe using SNe Ia, building on the advantages, for both statistical and systematic uncertainties, afforded by spectrum matching of the SNe. Such a survey is projected to reach a better statistical-plus-systematics cosmology measurement precision than all-imaging surveys: both options are systematics limited and the spectroscopy allows better systematics control (and both also achieve comparable statistical-only uncertainty). As Rubin et al (2022, arXiv:2206.10632) describes, such a prism+filters survey also makes it possible to measure the redshift of each supernova, avoiding the systematic errors and outliers of photometric redshifts. This balanced prism+filter survey also opens other static spectroscopic science opportunities, using the reconstructed forward-modeled fields that will be observed at ~50 different rotations over the course of the 2-year survey.

We here want to emphasize a new potential afforded by a prism survey, beyond the SN cosmology use: the spectroscopic discovery of transients. Of the many unique aspects of the RST WFI, its wide-field spectroscopic transient search capability is a real breakthrough, as there has never before been such a capability. An interesting advantage of a spectroscopic transient survey is that any fast transients can be characterized immediately from their spectra. With only imaging, one needs to trigger follow-up based on much more limited (potentially only one detection in one filter) information; if such a trigger requires space resources, it could well miss the subsequent evolution of such events while still bright. With its R~100 spectral resolution, corresponding to a restframe photospheric velocity of 3000 km/s, the prism observations will have significantly higher sensitivity for fast explosive transients than the grism that is being employed for the High Latitude Wide Area Survey, and will be cadenced. This potential is important to consider when designing the HLTDS. We suggest that the prism+imaging survey variant offers both the most systematics control for the SN cosmology measurements and the most flexibility and balance for transient science.
High Latitude Time Domain Survey large scale structure of the universe cosmology, spectroscopy, transients
gregory p skrivseth community Deep Field High Latitude Time Domain Survey Combine Roman's infrared abilities with JWST's infared since both of these are at L2.

If this is possible we could get a much better detailed view as the telescopes cadence through viewing area.

I only wonder if both are close enough to network and combine to make a "bigger" mirror.
High Latitude Time Domain Survey stellar physics and stellar types, the intergalactic medium and the circumgalactic medium n/a
Igor Andreoni University of Maryland Igor Andreoni, Michael Coughlin, Mansi Kasliwal, on behalf of a larger collaboration Kilonova Multi-Messenger Science with Nancy Grace Roman Space Telescope The joint detection of gravitational waves (GWs) and their electromagnetic transient counterparts marked a watershed moment in astrophysics. The first (and so far the only) binary neutron star merger with a confirmed counterpart was GW170817, which was discovered in association with a bright optical/infrared transient. The low electron fraction of neutron star merger ejecta favors the production of heavy elements such as lanthanides and actinides via rapid neutron capture (r-process). The decay of these unstable nuclei power the infrared-bright "kilonova". The identification of electromagnetic counterparts provides numerous benefits to GW analysis, including: improved localization leading to host-galaxy identification; determination of the source's distance and energy scales; characterization of the progenitor's local environment; breaking modeling degeneracies between distance and inclination; insight on the launching and propagation of relativistic jets, and the related emission processes; and insight on the formation channel of binary neutron star mergers. The discovery of a population of kilonovae will allow us to determine if neutron star mergers are the dominant sites for r-process element nucleosynthesis, place limits on the neutron star equation of state, and make independent measurements of the Hubble constant.

Roman will achieve a unique combination of wide field of view, depth and near-infrared sensitivity. These characteristics will enable Roman's discovery of counterparts that will be missed by optical telescopes, such as kilonova that are distant or with higher lanthanide fractions, higher mass ratios, observed from equatorial viewing angles, or dust obscured. We therefore recommend to (i) make available a Target of Opportunity mode for GW follow-up; (ii) possibly consider a cadence strategy better suited for serendipitous kilonova discovery in the time-domain survey footprint.
High Latitude Time Domain Survey stellar physics and stellar types neutron stars, binary stars, Supernovae
Jiangtao Li Purple Mountain Observatory & University of Michigan A high cadence monitoring of stellar variables in our massive neighbor Various types of variable stellar sources provide key information on stellar evolution in different galaxy environments. As the closest massive galaxy from the Milky Way, the Andromeda galaxy M31 provides us with an ideal laboratory to study the variability of many stellar sources at a high enough cadence in multi-wavelength. In particular, some strong variabilities of stellar sources can be detected in X-ray, optical, and/or near-IR bands on a timescale of <~10^2s. These short timescale variabilities are often produced in the accretion disk of the X-ray binary, the circum-stellar disk or the heated surface of the donor star, so are key probes of the accretion processes. Furthermore, we can also study the orbital variation of some types of binaries with multi-epoch observations at a cadence of once a few days. This helps us to constrain some key parameters of the binary stars. Compared to the optical band, the near-IR band is critical in tracing not only some low-mass and giant stars, but also the accretion disk in X-ray binaries.

In a sky area with a high spatial density of stellar sources, such as the nuclear region of M31, the optical/near-IR detection limit is often determined by the crowding effect instead of the signal-to-noise ratio. The high angular resolution of a space telescope such as the Nancy Grace Roman Space Telescope (formerly the WFIRST), is thus critical to lower the detection limit. Based on the existing HST near-IR observations, we expect the detection limit in J- or K-band could be >20mag in the very nuclear region of M31, within a single WFIRST exposure of ~55s. The detection limit can be much lower in outer regions less affected by the crowding effect (down to ~24-25mag in near-IR in a single WFIRST exposure). The large FOV of WFIRST, together with the high number density of detectable stellar X-ray sources in M31, further enable us to simultaneously monitor the multi-wavelength variations of many stellar sources in this unique laboratory.
High Latitude Time Domain Survey stellar physics and stellar types, stellar populations and the interstellar medium, galaxies, supermassive black holes and active galaxies Disk galaxies, Stellar populations, Low-luminosity active galactic nuclei, Binary stars / Trinary stars, Variable stars
Jiří Krtička Masaryk University Jan Janík, Zdeněk Mikulášek, Miloslav Zejda Search of black holes in wide binaries Stellar mass black holes can be detected in close binaries either from radial velocity surveys or thanks to tidal interaction detectable from photometry (Green et al. 2022). However, the corresponding signal due to black holes in wide binaries is too weak to be detected. Here we propose to use time-domain observations of chemically peculiar stars to detect stellar mass black holes in wide binaries.

Chemically peculiar stars are stars of upper part of main sequence that show strictly periodic variability due to surface spots modulated by rotation (alpha2 CVn variables). Dedicated long-term observations of these stars are able to detect even minute variations of their periods (Mikulasek et al. 2011). From such period variations, orbital motion due to unseen companions can be detected, including otherwise invisible black holes. Here we propose a dedicated time-domain survey of chemically peculiar stars to detect their unseen companions, most notably black holes. To get even very minute variations of orbital periods, observations of the fields already observed by Kepler (K2) and TESS would be needed.
High Latitude Time Domain Survey stellar physics and stellar types chemically peculiar stars, binaries, black holes
Justin Pierel STScI Armin Rest, Ori Fox, Sebastian Gomez, Mike Engesser, Lou Strolger, Suvi Gezari, Melissa Shahbandeh, Matt Siebert Enabling Precision NIR SN Ia Cosmology with the HLTDS Understanding dark energy is the frontier of modern cosmology, and a primary mission goal of the Roman Space Telescope. Precise measurements of the dark energy equation-of-state parameter (e.g., w), and its possible evolution with redshift (w0, wa), are fundamental to possibly resolving discrepancies between observed and theoretical values for the Hubble constant (H0), ruling out physics beyond ΛCDM, and constraining the fate of the universe. The most precise measurements of w in the dark energy dominated universe, which leveraged Type Ia supernovae (SNe Ia), concluded that disentangling SN color from dust was among the most significant systematic uncertainties remaining for dark energy measurements. Although the sample size of SNe Ia expected from the Roman HLTDS will be enormous, these systematics will remain.

Recent simulations attempting to provide an optimal HLTDS survey for SN Ia cosmology are only optimized at rest-frame optical wavelengths, even though Roman was in part designed because of the promise of NIR SN Ia observations. Roman can significantly (≳ 75%) reduce systematics related to dust by observing SNe Ia at rest-frame NIR wavelengths, where dust has little impact and SNe Ia are statistically ~ 60% more standard. The filter set of Roman will ensure some SNe Ia have rest-frame NIR observations, but based on current proposals it will be a small fraction (low-z SNe Ia found in the deep field) and only to z<0.9. We therefore propose to include the F184W (wide-field) and F213W (deep-field) filters in the HLTDS survey strategy, which would simultaneously provide rest-frame NIR information to z~1.3 and increase the parameter space probed by the HLTDS for all transients. The Roman HLTDS is the only means of obtaining a large sample (thousands) of high-precision (space-based) rest-frame NIR SN Ia observations that rivals optical surveys, as previous efforts with HST have only yielded ~dozens of SNe Ia due to the small FOV.
High Latitude Time Domain Survey stellar physics and stellar types Supernovae, dark energy, Infrared photometry
Michael Fausnaugh MIT AGN Dust reverberation mapping in the High Latitude Time Domain Survey The dominant paradigm of Active Galactic Nucleus unification (AGN unification) involves a dusty toroidal structure located about 0.1--1 parsec away from the central supermassive black hole to explain the difference between obscured (Type II) and unobscured (Type I) AGN. However, the detailed distribution of dust is poorly constrained, with a range of distances, covering fractions ("clumpiness"), opening angles/scale heights, and temperatures appearing in the literature. The picture of AGN unification based on the "dusty torus" has been further complicated in recent years with near-IR interferometric observations using GRAVITY (on the VLTs), suggesting polar outflow components that emit in the near- to mid-IR. Overall, these results cast uncertainty over the distribution of the dust close to the central AGN and suggest that the simple "torus" picture of AGN structure required for unification does not capture the full complexity of dust these systems. It is possible to constrain many of the properties of AGN dust with "Dust Reverberation Mapping", based on measuring light echoes of variations from the AGN accretion disk that are reprocessed at IR wavelengths by the dust. Modeling of the dust echoes can constrain the distance and geometry of the dusty structure, as well as the dust's distribution of temperatures and compositions. A unique opportunity exists to perform dust reverberation experiments using the Roman High Latitude Time Domain Survey. With expected cadence of a few days over several years (driven by requirements for Type Ia supernova discovery), the High Latitude Time Domain survey is perfectly matched to AGN variations on day-to-week timescales and the response of reverberating dust over month-to-year timescales. Roman AGN monitoring data will be obtained for free for an unprecedented number of AGN owing to Roman's wide field of view. Furthermore, Roman's deep limiting magnitudes will allow us to search for evolution in the dust structure as a function of redshift, which has implications for the number of obscured AGN in the universe that in turn inform our understanding of AGN evolution and supermassive black hole growth over time. The main parameter influencing the AGN dust science will be the question of filters used in the supernova survey. Furthermore, rarer AGN activity may be found for larger sky coverage. High Latitude Time Domain Survey supermassive black holes and active galaxies Reverberation mapping, Supermassive black holes, X-ray active galactic nuclei (Obscured), active galactic nuclei unification
Mitchell Karmen Johns Hopkins University Suvi Gezari A sweet spot for high redshift tidal disruption events in Roman We propose a wide, slow, and deep observing strategy for the Roman Space Telescope Core Community Survey to optimize tidal disruption event (TDE) science. Due the combination of its wide field of view and excellent near-infrared sensitivity, Roman is in a unique position to detect TDEs out to unprecedented redshifts. Given Roman's reported magnitude limits for the high latitude time domain survey, of 26.7 mag in F184 for a 900 second exposure and 26.5 mag in F158 for a 300 second exposure, and taking into account TDEs' characteristic thermal 30,000 K spectral energy distribution, and typical luminosity of M = -19 mag in the optical, we find that TDEs will be visible by Roman out to a maximum redshift of 7. Optically selected TDEs have thus far been limited to redshifts below z ~ 0.2, with only a couple of jetted TDEs observed out to z ~ 1.2. However in the near-infrared, the detection of high-redshift TDEs benefits from the K-correction, since the peak of their emission in the rest-frame UV is red-shifted into the near infrared. Particularly, in Roman's F184 and F213 bands they are brightest, and have no extinction from the Lyman-alpha forest. We have found a sweet spot for their detection with Roman by calculating TDE rates or a given filter and depth. These high-redshift TDEs will provide unprecedented insight into SMBH formation and cosmic evolution, and may be some of the only transients visible at redshifts greater than 6 with Roman. This contrasts from Type Ia supernovae, which due to their cooler spectral energy distributions are not detectable beyond z ~ 4. Additionally, the typical post-starburst galaxies in which TDEs occur will not be visible beyond redshift 3, making TDEs at high redshifts effectively "hostless" transients.

Given current empirical estimates of TDE rates from the local universe, we expect to observe a total of 0.92 TDEs/deg^2/yr in F184 to a depth of 26.7 mag, with 0.15 TDEs/deg^2/yr beyond redshift 5. To observe at least ten high-redshift TDEs, we require a wide and deep survey. Over the two years of the proposed high latitude time domain survey, we require 30 deg^2 of observing area to a depth of at least 26.7 mag in F184 and F213 to detect at least ten high-redshift TDEs. Due to the time dilation of the TDE light curves at these high redshifts, the events may take multiple observer-frame years, so a slow survey is preferred in order to observe the light curve of TDEs. Finally, the current high latitude time domain survey does not include observations in F213- which are essential for multi-wavelength observations of high-redshift TDEs. Colors of TDEs are useful in distinguishing them from QSOs, and co-added stacks of ten observations in F213 would allow us to reach a 28 mag depth in which we can observe TDEs with redshifts up to 10!
High Latitude Time Domain Survey supermassive black holes and active galaxies Supermassive black holes
Nao Suzuki Lawrence Berkeley National Laboratory Astro-Avengers Deep Field Survey on CDF-S : Mapping the Universe from Baryon to Dark Matter We propose a joint survey of the Roman, Euclid, LSST and Subaru HSC/PFS on Chandra Deep Field South (CDF-S). Hyper-Suprime Cam (HSC) and CFHT (u-band) observation on CDF-S is being carried out by us (H20: Hawaii 20 square degree Survey), and Euclid will observe this field as one of their deep drilling fields. Thus, optical (ugriz) to NIR (YJH) data can exist for 10 square degrees on CDF-S as well as grism data from Euclid. We aim to add narrow-band filter observation by Subaru HSC so that we can map out emission line galaxies at the epoch of reionization. And Prime Focus Spectrograph (PFS) on Subaru can observe all of the interesting objects in the field. If Roman CCS can observe CDF-S with all of the filters (F062-F213) with a certain cadence, it becomes a Rosetta Stone Field to the Astro Community. CDF-S is visible from all of the major telescopes in Hawaii and Chile (LSST, VLT, TAO) including ALMA, SKA and ELT. Compared to COSMOS, the IR background is low, and it is close to the Continuous Viewing Zone (CVS) of the Roman which has a great advantage for the cadenced survey for supernovae.

We demonstrate three major scientific goals.1) Because we will have enough background galaxies, we can map out 3D dark matter distribution at redshift 2-3. Using the Lyman alpha forest from the Break Galaxy Observation from PFS, we will have a 3D tomographic map of baryons. We can visualize how dark matter, baryons and galaxies are distributed in 3D space for 10 square degrees for the first time. We can finally test 3D simulation to the real universe. 2) Epoch of Reionization can be intensively studied by combining narrow-band filter observation, spectroscopic data and deep Roman IR imaging. All of the interesting high-z galaxies can be observed by JWST and ALMA. 3) Roman IR Transient survey would open a new window to investigate the high-z universe. Type Ia supernovae can reach up to z=2 and can probe dark energy at the time of matter dominated universe. The explosion of population III stars, known as pair-instability supernovae, can be found in 10 square degrees. Besides the above three examples, many science goals can be achieved and it would become the most valuable data set in astronomy for many decades to come. Thus it would be the best choice for CCS.
High Latitude Time Domain Survey galaxies, the intergalactic medium and the circumgalactic medium, supermassive black holes and active galaxies, large scale structure of the universe Large-scale structure of the universe, Reionization, Supernovae, Lyman-alpha forest, High-redshift galaxies
Ori Fox STScI Isobel Hook, Anton Koekemoer, Takashi Morina, Eniko Regas, Armin Rest, Lou Strolger, Lifan Wang An Extended Time-Domain Survey (eTDS) to Detect High-z Transients, Trace the First Stars, and Probe the Epoch of Reionization Transient astronomy in the z>4 Universe is an unexplored domain that offers the possibility of probing high-redshifts, the first stars, and the epoch of reionization. Isolated Pop III stars remain mostly beyond the reach of any current observatory, but Roman's unique combination of field of view, depth, multi-year baseline, and wavelength access allow us, for the first time, to detect the explosions from these early massive stars. A high-z transient survey can (1) unveil core-collapse (CCSNe), super-luminous (SLSNe), and pair-instability supernovae (PISNe) from Pop III stars, (2) test Initial Mass Function (IMF) scenarios at high-z, and (3) to provide the first direct constraints on the contribution of these massive stars to the reionization of the Universe.

We will highlight in our upcoming White Paper in detail with figures that while high-z transient science is not a primary driver of the current Roman Core Surveys, it is a natural consequence. The Roman Deep High-Latitude Time Domain Survey (HLTDS) already provides a powerful ability to detect explosive transients, but we propose that that extending the current HLTDS in both time (Cycles 1 & 2) and wavelength (K band) is needed to color select high-z events. An extended TDS (eTDS) can generate an unparalleled transient database in terms of combined supernova (SN) redshift reach, area, and timescale. It would make Roman a discovery engine for rare, extreme high-z SNe and, for the first time, build a sample of thousands of normal high-z core-collapse (CC) SNe. Just as the GOODS observing strategy of repeated visits was designed to serve both time-domain and deep static-sky science, the eTDS will provide exceptionally deep and wide imaging comparable to COSMOS-Webb in depth (F158 ~ 29.5/F213 ~ 27.5 mag), but 8 times larger in area! eTDS costs ~360 hours, a small fraction of HLTDS.
High Latitude Time Domain Survey stellar physics and stellar types, large scale structure of the universe Supernovae, Massive stars, Stellar Phenomena , Reionization, Extragalactic Legacy And Deep Fields
Peter Nugent LBNL / UC Berkeley Nao Suzuki Enhanced Transient Science with Roman + LS4 The The La Silla Schmidt Southern Survey (LS4) is a 5 year public, wide-field, optical survey using an upgraded 20 square degree QUEST Camera on the ESO Schmidt Telescope. LS4 will have first light at the end of 2023 and the survey will commence in early 2024. We will use LBNL fully-depleted CCDs to maximize the sensitivity in the optical up to 1 micron. This survey will complement the Legacy Survey of Space and Time (LSST) being conducted at the Vera C. Rubin Observatory in two ways. First, it will provide a higher cadence than the LSST over several thousand square degrees of sky each night, allowing a more accurate characterization of brighter and faster evolving transients to 21st magnitude. Second, it will open up a new phase-space for discovery when coupled with the LSST by probing the sky between 12-16th magnitude - a region where the Rubin Observatory saturates. The science goals of LS4 include obtaining a large sample of nearby supernovae to probe both supernova physics and cosmology including peculiar velocities; follow up of multi-messenger astrophysical transients including gravitational wave events, GRBs, and neutrinos; tidal disruption events; AGN and quasar variability studies; stellar physics in the Milky Way; and other unexpected short duration transients. Through coordination with Roman, and joint analysis of the data, we would be able to extend the science reach of both projects considerably in a similar way to what we have proposed doing with the LSST on Rubin - here extending the science impact to the near infrared. High Latitude Time Domain Survey stellar physics and stellar types, galaxies, supermassive black holes and active galaxies, large scale structure of the universe supernova, Variable stars, AGB, GRB, Cosmological parameters
Ryan Hickox Dartmouth College Low-mass AGN through optical variability in the High Latitude Time Domain Survey Identifying growing central supermassive black holes (SMBHs) in low-mass galaxies provides a valuable constraint on the cosmic evolution of SMBHs and their ultimate origin in the early Universe. Recently, optical variability studies using sensitive, high-cadence photometric studies have been used to identify AGN in low-mass galaxies (e.g., Baldassare et al. 2020, ApJ, 896, 10). However, these studies have mostly been limited to the nearby Universe due to the need to spatially resolve the center of the galaxy to identify low-amplitude (< 0.1 mag) nuclear variability. Rubin/LSST will provide high-cadence light curves for a very large area, but is still limited by atmospheric seeing in resolving nuclei at higher redshifts.

The Roman High Latitude Time Domain Survey (HLTDS) is well-suited to detect nuclear variability in low-mass galaxies, allowing identification of their nuclear black holes at cosmological redshifts. The high photometric sensitivity and sharp resolution (reaching galaxy nuclear flux limits of ~23.5 mag for ~2% sensitivity; Wang et al. 2022; arXiv:2204.13553) will allow identification in AGN in dwarf galaxies (stellar mass ~ 10^9 M_sun) out to z~0.3 (extrapolating from Baldassare et al. 2020), a volume of similar size to that of SDSS at z < 0.04. The characteristic timescales of AGN as modeled by a damp random walk have been found to depend on BH mass (Burke et al. 2021, Science, 373, 789) corresponding to ~tens of days for M_BH between 10^5 and 10^6 M_sun, well-matched to the necessary cadence for the cosmological supernova survey. Since these AGN are detected via time variability more so than color information, to optimize the number of low-mass AGN, the HLTDS would benefit from a larger area covered by fewer filters or (somewhat) lower cadence. However exciting science is likely to emerge from any survey optimized for SN discovery and characterization.
High Latitude Time Domain Survey galaxies, supermassive black holes and active galaxies Supermassive black holes, AGN host galaxies, Dwarf galaxies
Sam Grunblatt Johns Hopkins University Measuring Distances to The Edge of Our Galaxy and Beyond With TRGB Star Oscillations Stars near the tip of the red giant branch of stellar evolution oscillate with frequencies which are directly correlated with their luminosity and surface gravity. These pulsations have timescales of days to weeks, and thus can be observed in a survey with 5-day cadence over a 2 year baseline. As these stars are so intrinsically bright, observations in a filter between 1 and 2 microns that achieve 10 parts per thousand precision of a 18th magnitude star in H-band can be used to measure the oscillations and thus distances of stars hundreds of kiloparsecs away. These distances can then be used to determine the effective stellar 'edge' of the Milky Way, beyond which no more halo stars are found, important for understanding the formation of our Galaxy and the role of dark matter in shaping its potential. Furthermore, these observations can provide precise distances to nearby galaxies, and will also allow measurement of the distances to stars associated with the Andromeda Galaxy. These observations can be use as benchmarks for determining the potential of the Local Group with implications for galactic dynamics at several Mpc distances. High Latitude Time Domain Survey stellar populations and the interstellar medium evolved stars, stellar distances, galaxy halos
Sebastian Gomez Space Telescope Science Institute Suvi Gezari (STScI/JHU), Armin Rest (STScI/JHU), Yossef Zenati (JHU), Griffin Hosseinzadeh (Arizona), Daichi Hiramatsu (CfA), Qinan Wang (JHU), Peter Blanchard (Northwestern), Ryan Foley (UCSC), Melissa Shahbandeh (JHU/STScI), Justin Pierel (STScI), V. Ashley Villar (PSU), Charlie Kilpatrick (Northwestern), Tarraneh Eftekhari (Northwestern), David Jones (NOIRLab), Tamás Szalai (U. of Szeged, Hungary), Eniko Regos (Konkoly), Jacob Jencson (JHU/STScI) The High Latitude Time Domain Survey for the Photometric Study of all Extragalactic Transients The Roman High Latitude Time Domain Survey (HLTDS) was conceived to detect SNe Ia out to large redshifts for the study of cosmology. Here, we argue that the HLTDS can be a revolutionary survey not only for the study of SNe Ia, but for all other types of either well-known, exotic, or undiscovered extragalactic transients. While the availability of the grism and prism will be of critical importance, we will focus here only on the photometric recommendations of the survey, for the sake of brevity. The study of extragalactic transients, as well as the discovery of yet unknown classes of transients, is of paramount importance for a very wide range of science cases. This was clearly reflected in the Astro2020 Decadal, which determined the study of the "Dynamic Universe" to be one of the top priorities of the field for the coming decade.

The discovery of Kilonovae (KNe) proved the link between neutron star mergers and Gamma-ray bursts, as well as the origin of heavy elements such as gold or platinum; future studies of KNe will help us pin down the neutron star equation of state, and allow us to use them as standard sirens to constrain the value of $H_0$. Tidal Disruption Events (TDEs) provide a critical avenue to study supermassive black holes, measure their masses, and understand the environments in the cores of galaxies. Superluminous Supernovae (SLSNe) are some of the most energetic explosions in the universe thought to be the end stages of the most massive stars, and getting a grasp on these explosions will lead to a better understanding of stellar evolution. Finding Type Ia SNe at high redshifts will allow us to have better constraints on cosmological models. The study of Type II SNe provides us with insights into both the circumstellar medium (CSM) surrounding red supergiants, as well as the different mass-loss scenarios leading up to their explosion. Stripped-envelope supernovae (SNe~Ib/c) teach us about mass loss in very massive stars and mass transfer due to binary interaction. Interacting supernovae (SNe~Ibn/Icn/IIn) probe extreme mass-loss in core-collapse progenitors, including asymmetry and shock physics. Pair Instability Supernovae (PISNe) are thought to be the end stage of Pop.\ III stars, yet their conclusive discovery remains elusive; searching for them at higher redshifts might prove to be successful. Finally, with any new survey comes new classes of transients we were not even expecting, some of which could surely be revolutionary for the field.

The landscape of extragalactic transients as it stands today spans a wide range of parameter space. KNe fade within a few days, while SLSNe can remain visible for hundreds of days. TDEs and SLSNe appear blue at early times, at a phase when radioactively powered SNe can appear quite red. TDEs tend to occur in the cores of green valley (E+A) galaxies, core-collapse SNe (CCSNe) can happen virtually anywhere in star-forming galaxies, while calcium-rich transients are predominantly found at large separations from elliptical galaxies. Pair Instability Supernovae (PISNe) remain elusive, Fast Blue Optical Transients (FBOTs) are still rarely discovered, and three out of every four SNe discovered is a SNe Ia. The study of any specific type of transient therefore requires critical optimization of filters and cadences, as well as a less critical balance between survey area and depth. Having a wide length of time between epochs will help us target SLSNe and PISNe, and a fast daily cadence is the only way to characterize KNe and FBOTs. Similarly, while the F213 filter will be useful for discerning SNe Ia from CCSNe, rest-frame $u$-band has proven to be instrumental in identifying TDEs. Despite their differences, the key metrics that are relevant for all transients are: finding them early, finding as many of them as possible, being able to identify their color, and finally having photometry from before, during, and after their peak. This is not a recommendation for a specific set of filters, cadences, areas, or depths, but a note that their ultimate choice should take into account these metrics for all types of extragalactic transients, not just SNe Ia, as these will subsequently affect all other related fields of astronomy.
High Latitude Time Domain Survey stellar physics and stellar types, supermassive black holes and active galaxies supernovae, supermassive black holes, stellar evolution
Toru Yamada ISAS, JAXA Deep Variability Search for Low-Luminosity AGN at High Redshift to Identify Very Low-Mass Black Holes in Galaxies Identifying very low-mass SMBH (10^5-10^7 Msun) at intermediate and high redshift is essential in understanding the physical history of co-evolution of SMBH and galaxies, especially for the early stage of their formation and growth. It is also important to identify SMBH of this mass range to understand co-evolution of central BH in bulges of disk galaxies. Variability survey is one of the most useful and currently a unique method to identify very low-luminosity AGN with such low-mass SMBH. So far the deepest multi-color variability surveys (e.g., Kimura et al. 2020 using the data of the Subaru Ultradeep HSC Survey) reach ~10^6-10^7 Msun SMBH at z=0.5-3. Roman High Latitude Time Domain Survey (HLTDS) can go deeper with much homogeneous and the controlled time cadence.

Roman HLTDS may cover ~5 deg^2 in the Deep and ~20 deg^2 in the Wide Survey (Rose et al. 2021). Single-epoch depth is ~26.5 (YJFK) and ~25.5 (RZYJ) (S/N=10 for Point Source), respectively. This is already ~2 mag or ~1 mag deeper than the deepest Subaru HSC variability AGN search with significantly larger area coverage. It is essential to investigate the correlation between the light curves of the candidate objects in the different band to identify the true sources among the numerous false positives. As the variability search selects type-1 AGN, the velocity width of the broad line can be measured by future spectroscopy with ELTs. Roman images are also essential in separating the AGN component from their host galaxies, to evaluate the average AGN luminosity which is also essential in BH mass measurement.
High Latitude Time Domain Survey supermassive black holes and active galaxies SMBH, AGN, galaxies, formation, coevolution
Veli Albert Kallio Sea Research Society The cosmic microwave background (CMB, CMBR) non-uniformity polarity test The cosmic microwave background (CMB, CMBR) is microwave radiation which is almost uniformly scattered throughout the space. However, it is almost uniformly scattered but not exactly uniform. This test proposes to that Deep Space images are taken from opposing anisotrophy polarities for investigation under magnification glass to see wheter there are galaxy field distribution differences between them. Would it be the cause that the density in the observed galaxy field causes variation that is then tied to anisotrophy in background radiation observed. Temperature inhomogeneties might correlate to the observed density of galaxy field and its radiations possible resonance with universe's matter in said directions.

Thus I suggest that incrementally higher background temperature may be observable where galaxy field is somewhat denser than in those regions where temperature inhomogeneties point towards lower temperatures. This could suggest resonances from radiation of the galaxies scattering from black matter, particles, or from intergalactic atom fields in vacuum. Another possibility is that universe's anisotrophy in background radiation is self-regulating in a way that universe is prevented from overheating by Droppler shifts controlling intensity of photons with the Droppler Shift stretched radiation providing a cooling mechanism to maintain balance. This could mean that denser galaxy fields move faster away with higher Droppler Shift to red, while parcel populated sections taking distance at slower pace (but with more intense photons of shorter wavelenght). Overall balance is always maintained either way.
High Latitude Time Domain Survey large scale structure of the universe galaxy field, Droppler shift, temperature inhomogeneties, resonance, expansion mechanisms
Yuichi Harikane University of Tokyo Masami Ouchi Studying the Cosmic Dawn at z>10 with Roman Understanding the galaxy formation in the early universe is one of the frontiers of modern astronomy. Recent JWST observations have found many galaxies at z>10 whose number density is surprisingly higher than theoretical model predictions, suggesting a possibility that the physics in the early galaxy/star formation is fundamentally different from that in lower redshift universe (e.g., see discussions in Harikane+23, ApJS, 265 5). However, due to the small field-of-view of JWST/NIRCam, the number of such high redshift galaxies is limited, which prevents us to conduct statistical studies.

Here, we propose to include the F158, F184, and F213 imaging observations in the Roman High Latitude Time Domain Survey. By achieving the depth of 27.2 ABmag (F213-band, 5sigma, point source, see Harikane+'s white paper for the Early Definition Survey), the High Latitude Time Domain Survey will provide samples of 2000 and 7-100 galaxies with MUV<~-21 mag at z=12-14 (F158-dropout) and z=14-16 (F184-dropout), respectively, allowing us to investigate the bright-end of the UV luminosity functions and massive galaxy formation in the early universe at z>10 with unprecedentedly large survey volumes that JWST/NIRCam cannot reach. Thanks to their brightness, we can not only conduct statistical studies (e.g., UV luminosity function, cosmic SFR density), but also investigate detailed properties (e.g., chemical properties, dynamics, stellar populations) by spectroscopically following up these galaxies using JWST/NIRSpec, MIRI, and ALMA. By including these observations whose total observing time is less than 10% of the entire survey, we can efficiently add valuable science cases for early galaxy formation in this core-community survey.
High Latitude Time Domain Survey galaxies Galaxy evolution, Galaxy formation, High-redshift galaxies
Yuichi Harikane University of Tokyo M. Oguri (Subaru Advisory Committee, Chair), T. Kodama, M. Ouchi, A. Nishizawa, H. Miyatake, Tsutomu T. Takeuchi, K Nakajima, Tomomi Sunayama、Masayuki Tanaka, A. K. Inoue Maximizing the Synergy between Roman and Subaru The combination of joint Roman and Subaru observations has the potential to enable transformative science that cannot be done by either telescope alone. The wide field of views of Subaru/Hyper Suprime-Cam (HSC, 1.5 deg2) and Prime Focus Spectrograph (PFS, 1.2 deg2) have excellent synergies with Roman's wide field instruments. Roman will image the 0.6-2.1um sky with unprecedented depth and area, and Subaru/HSC will provide broad-band and unique narrow- and medium-band images at 0.4-1.0 um complementary to Roman. The Subaru/PFS will conduct massive spectroscopic observations (~2400 fibers/pointing) with the medium resolution (R~3000) at 0.38-1.26um, which will complement Roman's grism spectroscopy at 1.0-1.9um with R~300. The director of the Subaru Telescope and Subaru Advisory Committee already agreed with NASA to commit 100 Subaru nights to the Roman-Subaru synergetic observations.

To enable the Roman and Subaru synergetic observations, we propose to observe northern and equatorial fields that can be observed with Subaru. The possible field candidates include Chandra Deep Field South, North Ecliptic Pole, and COSMOS, all of which are accessible from Subaru and with low Galactic extinction. By taking advantage of the unique capabilities of Subaru/HSC and PFS, the Roman and Subaru/HSC+PFS synergetic observations will allow us to investigate various important science cases to understand galaxy formation and evolution, such as discoveries of luminous early galaxies at z>10 (with deep non-detection bands from Subaru to eliminate interlopers) currently showing a tension with theoretical predictions, large scale structures and protoclusters at z=2-15, mapping the progression of cosmic reionization with improved redshift precision of galaxies enabled with HSC/narrow-bands+Roman, the most massive galaxies to study their possible tension with the LCDM cosmology up to z~4, and metal-poor star-forming galaxies in the early evolutionary phase at z=1-2 possibly hosting primordial structures such as Pop-III stars, all of which can be only identified in the wide-area Roman and Subaru synergetic observations. Furthermore, the medium-band images from Subaru/HSC will greatly improve the accuracy of the photometric redshift which is crucial for weak lensing cosmology. Thus, choosing fields that can be accessible from Subaru as the core community survey field will maximize the scientific outputs from Roman and Subaru synergetic observations.
High Latitude Time Domain Survey galaxies, the intergalactic medium and the circumgalactic medium, supermassive black holes and active galaxies, large scale structure of the universe Galaxy evolution, Galaxy formation, Cosmology, Large-scale structure of the universe, Reionization
Zoltan Haiman Columbia University Tamara Bogdanovic, Alessandra De Rosa, Daryl Haggard, Xin Liu, Delphine Porquet, Alberto Sesana, Jonathan Zrake Massive Black Hole Binaries in the High Latitude Time Domain Survey Massive black hole binaries (MBHBs) are thought to frequently arise in galactic nuclei, including active galaxies, as a result of the hierarchical build-up of galaxies. These MBHBs are the primary targets for LISA in GWs. The same population of binaries, at somewhat earlier stages of their merger, with larger separations, should be discoverable in time-domain electromagnetic surveys, such as Roman's High Latitude Time Domain Survey. While there exist several dozen candidates, identified based on their periodicities, they remain controversial. This is primarily because stochastic red noise can mimic periodicity when only a few cycles (typically of order a year) are observed.

At m~26 mag, roughly 2 magnitudes deeper than LSST's single-visit detection limit (depending on the filter), the extrapolation of the quasar luminosity function suggests that the High Latitude Time Domain Survey should contain about ~30,000 quasars, as well as additional low-luminosity active galactic nuclei (AGN). This should permit a detailed study of AGN variability, and to search for MBHBs among these AGN with GW inspiral times of as small as ~10^4-10^5 years, where the binaries are safely in the GW-driven stage. Taking 10^6 Msun as the approximate BH mass corresponding to Roman's detection threshold, this corresponds to an orbital period of ~6-14 days. The short periods would allow the detection of a large number of cycles and securely rule out fake periodicity from red noise. In the GW-driven regime, discovering several dozen or more sources with a range of periods would allow a novel test of the GW inspiral time, since the number of sources should scale with their period as ~P^8/3. Finally, identifying this short-period MBH population would provide a unique synergy between Roman and LISA: these sources are precursors to LISA events, and will yield robust constraints on the LISA merger rate. To facilitate this, it would be good to have a cadence of order 1-2 days (for a few points per period), and it would be useful to have at least two or three different filters, to help distinguish periodic binary variability from other possible periodic AGN variability. Having this cadence would also enable the discovery of periodic flares from partial tidal disruptions (TDEs), which would be relevant for understanding the population statistics of extreme mass-ratio inspirals (EMRIs), another prime class of targets for LISA.
High Latitude Time Domain Survey supermassive black holes and active galaxies High-luminosity active galactic nuclei, Low-luminosity active galactic nuclei, Quasars, Supermassive black holes, Gravitational waves
A. Kashlinsky SSAI, Observational Cosmology Lab, Goddard Space Flight Cntr R. Arendt, M. Ashby, F. Atrio-Barandela, M. Strauss Precision probing the dipole of the cosmic infrared background The cosmic microwave background (CMB) dipole is the oldest known CMB anisotropy measured by now with the unprecedented precision of S/N ~ 200. It is conventionally interpreted as being fully of kinematic origin due to the Solar System moving at velocity VCMB = 370 km/sec in the direction of (l, b)CMB = (263.85+/-0.1, 48.25+/-0.04) deg. The fully kinematic origin of the CMB dipole is further motivated theoretically by the fact that any curvature perturbations on superhorizon scales leave zero dipole because the density gradient associated with them is exactly cancelled by that from their gravitational potential. However, already prior to the development of inflationary cosmology there were suggestions that the CMB dipole may be, even if in part, primordial. Within the inflationary cosmology, which posits the non-Friedmann-Lemaitre-Robertson-Walker (FLRW) metric on sufficiently large scales due to the primeval (preinflationary) structure of space-time, such possibility can arise from isocurvature perturbations induced by the latter and/or from entanglement of our Universe with other superhorizon domains of the Multiverse. Hence, establishing the nature of the CMB dipole is a problem of fundamental importance in cosmology.

It is important to establish observationally the fully kinematic nature of the CMB dipole and whether the homogeneity in the Universe as reflected in the FLRW metric models is adequate to describe what we observe. The dipole of the integrated light of galaxies (IGL) provides a measure of the kinematic cosmic dipole. Subtraction of the implied velocity vector from that of the CMB can reveal if a non-kinematic component of the CMB dipole exists. The technique is enabled by 1) the amplification of the CIB dipole due to the Compton-Getting effect, coupled with 2) the large sky areas and galaxy samples obtainable with the Roman Core Community Survey. While this technique will be applied to the Euclid Wide Survey, the Roman mission will have important differences and, if done properly, will have advantages, by 1) probing galaxies to fainter magnitudes over a given area so a larger galaxy sample is assembled reducing the statistical noise in the dipole measurement, and 2) having two photometric bands (F184 and F213) where extinction is lower than at the Euclid-probed wavelengths. Hence it is important that the CCS includes F184 and F213 measurements and samples fields sufficiently far apart in both hemispheres such that all three vector components of the IGL dipole can be measured with accuracy sufficient to probe any offset from the kinematic CMB dipole to better than 1 deg.
High Latitude Wide Area Survey large scale structure of the universe Cosmology, Large-scale structure of the universe, Cosmic infrared background
A. Kashlinsky SSAI, Observational Cosmology Lab, Goddard Space Flight Cntr R. G. Arendt Source-subtracted cosmic infrared background fluctuations The Cosmic Infrared Background (CIB) is the collective radiation emitted throughout cosmic history, including from sources largely undetectable by current or future telescopic studies. Theoretical models predict that at redshifts z > 30, the emergence of the first stars, supernovae and black holes rapidly transformed the hitherto featureless universe into an increasingly complex state. While these objects will remain largely inaccessible to individual detection with future telescopes, they may be detectable via their recognizable contribution to the source-subtracted CIB fluctuations remaining after subtracting foreground sources to sufficiently low levels. The authors are already conducting such an investigation on Euclid in the framework of the LIBRAE (Looking at Infrared Background Radiation Anisotropies with Euclid) project, one of 3 selected by NASA run on ESA's Euclid ( Through the Euclid and Roman observations, and cross correlation with backgrounds at other wavelengths, the measurements will provide highly important and new information on when and where the first galaxies formed in the Universe. Collectively, here one measures all the objects out to very high redshifts, not just those at the very highest luminosities that might number in the tens or hundreds in the resolved sources. This experiment significantly expands Roman's scientific reach by probing all the emissions produced as the Universe emerged from the "Dark Ages", including from sources inaccessible to its contemporary JWST, which probes only the very brightest objects at z >~ 10.

Roman will have some advantages over Euclid here: 1) its survey will probe foreground galaxies some 2 magnitudes deeper than Euclid's Wide Survey, and 2) the data will extend to longer wavelengths (F184, F213 filters). These advantages have the potential for transforming the CIB field into a new area of precision cosmology and so must be explored.
High Latitude Wide Area Survey large scale structure of the universe Cosmology, large-scale structure of the Universe, cosmic infrared background
Aaron Meisner NSF's NOIRLab A New Window into the Milky Way's Structure and History Modern optical surveys have enabled tomography of the Milky Way using populations such as main sequence turnoff stars. The Milky Way's cold, substellar population also carries a wealth of information about our Galaxy's structure and the star formation process at low masses, but thus far studies of these coolest objects have been limited to the Sun's very local neighborhood. The combination of deep near-infrared and red-optical survey data from Roman and Rubin will vastly expand the volume covered by samples of cold (sub)stellar objects, allowing us to: map the Galaxy's scale height into the L and T spectral classes, understand any metallicity dependence toward the bottom of the substellar mass function, characterize the stellar/substellar boundary's evolution with metallicity, trace low-mass star formation over cosmic time, and probe the age versus temperature relation of brown dwarf cooling.

Sample selection will be a primary challenge in this endeavor. Rubin naturally complements Roman in identifying distant substellar objects, through the extended wavelength coverage it affords into the optical and the lengthened Roman+Rubin time baseline available for proper motions. Tools for joint analysis of Roman+Rubin survey data archives would help enable this science case, particularly cross-matched catalogs, homogenized astrometry, and ideally "forced photometry" of each survey's detections in the other's imaging. It is important for this science application that the Roman High Latitude Wide Area Survey include imaging in Roman WFI's K-band equivalent filter (F213), as this bandpass is critical for photometric selection of brown dwarfs, particularly distant ultracool dwarfs in the Milky Way's thick disk and halo (see e.g., Figure 1 of Stauffer et al. 2019, BAAS, 51, 94).
High Latitude Wide Area Survey stellar physics and stellar types brown dwarfs, infrared photometry, low mass stars, late-type stars, astrometry
Adam Leroy Ohio State University Francesco Belfiore (Arcetri), Eric Emsellem (ESO), Erik Rosolowsky (U Alberta), Eva Schinnerer (MPIA) Roman should make a complete survey of stellar clusters, associations, and massive stars across the nearby galaxy population as a major part of its core community surveys The resolution and field of view of Roman offer an unprecedented opportunity to identify and resolve stellar clusters and associations, find individual bright stars, trace out transient phenomena, and even map out signatures of the interstellar medium (in attenuation) over the full area and full population of nearby galaxies. These clusters and associations are critical outputs of the star formation process, important sources of stellar feedback, and - as relatively simple systems - can serve as markers of the star formation history or "clocks" that can be used to understand timescales of the process of galaxy evolution. Meanwhile, in nearby galaxies, inventories of individual, giant stars allow us to establish high quality distances and map out the progenitors of essentially all future supernovae and unlock the potential of the time domain over a much broader part of the galaxy population than is currently accessed from the ground.

To exploit these capabilities, the core community science should include an ambitious program that uses the Wide Field Instrument to imaging the full set of relatively massive galaxies out to the Virgo cluster in a broad suite of the filters. Over the last ~20 years, Hubble has made enormous investments (ANGST, GOALS, LEGUS, PHANGS) to map the cluster and stellar populations in a small area and modest subset of these nearby galaxies. These have been incredibly productive but still only scratched the "tip of the iceberg" in terms of combined spatial coverage and sampling of the full galaxy population. There is still debate about the absolute mass limit of a stellar clusters, which environments promote the formation of clusters and super star clusters, the fraction of stars formed in clusters, and how long stellar clusters can survive. The same observations that address these issues will yield major new insights into the globular cluster population of individual galaxies, yield precise distances to all targets, and even allow a stunning sharp, attenuation-based view of the ISM. Together these measurements imply immense legacy value to a wide range of communities that will not be replaced by any future mission.

With an ambitious, well-designed survey, Roman should be able to map out all of the star clusters in the local volume, measure their sizes and make good estimates of their masses and ages, identify the progenitor of every future supernova, and yield TRGB distances. It can do all of this while also pursuing satellite and stream-related science that is critical to the dark matter-oriented portion of the community. Roughly speaking, a wide field map of all ~ 200 massive galaxies out to Virgo in five filters at 30 minute depth is less than a month of time, would completely revolutionize this field, and would demonstrate long-term legacy value to a broad set of scientific communities

The US Decadal identified understanding the drivers of galaxy growth and unraveling cosmic ecosystems as top priorities for the coming decade. More generally, understanding the details of the "matter cycle" in galaxies has become a main focus across redshift. By including this kind of ambitious survey as part of the core community science, Roman would ensure enormous synergies with JWST, ALMA, the ngVLA, the SKA and its precursors, and a host of major optical observatories and would build directly on Hubble's ground-breaking work on and incredible legacy of cluster science. While the lack of the UV and bluest bands is certainly an issue for aspects of this field, it is certainly surmountable using clever cross-scale work and statistical techniques and - even more likely - by pairing Roman with the likely missions such as CASTOR or UVEX.
High Latitude Wide Area Survey stellar populations and the interstellar medium, galaxies Disk galaxies, star clusters, galaxy evolution, stellar distance, irregular galaxies
Akio Inoue Waseda University GREX-PLUS mission team Enhancing the value of Roman Core Community Surveys with GREX-PLUS wide-area imaging surveys in wavelengths longer than two micron The Roman Space Telescope will conduct unprecedented wide-area surveys in near-infrared wavelengths up to 2 micron. However, there are many important science cases achievable if the Roman survey is supplemented by similarly wide-area surveys in wavelengths longer than 2 micron. An extension of the spectral coverage of objects detected in the Roman surveys to better understand their spectral energy distribution is the simplest benefit. There should also be many populations not detected in Roman images but detected in wavelengths longer than 2 micron, such as extremely low temperature stars, dust-obscured stars, dusty high redshift galaxies and active galactic nuclei, and even star-forming galaxies at extremely high redshifts beyond redshift of 15. While the James Webb Space Telescope has the extremely high sensitivity in the wavelength range, it may not achieve any survey with a more than square degree area due to the narrow field-of-view. A Japanese future space telescope mission candidate, GREX-PLUS (Galaxy Reionization EXplorer and PLanetary Universe Spectrometer) plans to have a wide-field camera in a wavelength range of 2 to 8 micron and aims to conduct ~10--1,000 square degree wide-area imaging surveys. The imaging depths are ~27--24 AB magnitude depending on the survey area and the wavelength band. Although these depths are somewhat shallower than those of the Roman surveys, the wide-area survey ability of GREX-PLUS in wavelengths longer than 2 micron is only the solution to supplement the longer wavelength coverage to the Roman surveys limited to 2 micron. The target launch year of GREX-PLUS is early 2030s.

To maximize the synergy of the two wide-field imaging surveyors, Roman and GREX-PLUS, both telescopes should observe the same areas. Since GREX-PLUS will also orbit around the Sun-Earth L2 point, as will Roman, the sky area visibility will be the same. Therefore, GREX-PLUS will observe the sky areas where Roman observed in its Core Community Surveys and in General Observer programs for extragalactic fields and for the Galactic plane as well. Since there is a partial spectral overlap between Roman's F213 filter and GREX-PLUS's F232 filter, it would be highly beneficial to coordinate the Roman F213 imaging observations with the GREX-PLUS surveys in respect to the depth and area.
High Latitude Wide Area Survey solar system astronomy, exoplanets and exoplanet formation, stellar physics and stellar types, stellar populations and the interstellar medium, galaxies, the intergalactic medium and the circumgalactic medium, supermassive black holes and active galaxies, large scale structure of the universe n/a
Anowar Jaman Shajib University of Chicago The core-cusp problem and stellar initial mass function with strong lensing: Roman's HLWAS unveiling a new mass range for studying galaxy evolution Strong lensing is a powerful probe of the mass distribution in the lens galaxy. Thus, strong lensing provides insights into the properties and evolution of these galaxies. For example, resolving the core-cusp problem and estimating the stellar initial mass function (e.g., Shajib et al. 2022). Roman's HLWAS will benefit these science cases by discovering many new lens systems. They will include small-separation lenses thanks to the diffraction limit, unlike ground-based surveys. Thus, Roman lenses will span a low-mass regime yet unexplored with strong lensing.

The imaging and spectroscopy components of HLWAS will suffice to confirm lenses. Thus, high-resolution imaging and spectroscopic follow-up will not be necessary for confirmation. Roman's high-resolution imaging will also allow detailed lens modeling. The spectroscopic component will measure the redshifts for the lens and the source up to z ~ 2.77. The lensed arcs appear brighter in shorter wavelengths relative to the lens galaxy's light at that position. Thus, prioritizing shorter wavelength bands will help identify more short-separation lenses. Going for a deeper survey will help increase the redshift range of the discovered lenses. Such a high range of redshift will be helpful for galaxy evolution studies. Thus, Roman's HLWAS will be transformative for studying galaxy evolution with strong lensing at the low-mass regime.
High Latitude Wide Area Survey galaxies Elliptical galaxies, Galaxy dark matter halos, Galaxy evolution, Galaxy structure, Stellar populations
Armin Rest STScI Fox, O.; Shahbandeh, M.; Pierel, J., Gomez, S.; Siebert, M.; Jencson, J.; Strolger, L.; Gezari, S.; Foley, R.; Macias, P., Narayan, G., Coulter, D. Transient Exploration in the High Latitude Survey (TEHLS) Transient astronomy in the IR remains mostly an unexplored domain, since ground-based surveys are limited by the effects of the atmosphere, and space-based surveys have been lacking in both depth or area. The launch of JWST finally offered us the possibility to look into the IR to unprecedented depths, but the FOV is small (<1 square degree), which makes it difficult to obtain significantly large samples or find rare objects. With the wide-field capabilities of Roman, we will be able to go a step further and probe the transient IR Universe at scales of 10s to 1000s of degrees.

The Roman High Latitude wide area Survey (HLS) will give us the opportunity to explore the transient IR Universe at a whole different level, provided the right observing strategy is chosen. While the HLS is not currently designed as a time-domain survey, there is great value in splitting up the observations into two epochs to create a time-domain aspect that we name Transient Exploration in the High Latitude Survey (TEHLS). In transient astronomy, there are two ways to build a sample: depth or area. While the High Latitude Time-domain Survey (HLTDS) already exists and is designed to go much deeper, our proposed TEHLS wins on sheer area of the sky. With over 1700 deg^2, TEHLS probes a unique region of phase space that requires a large area of sky to generate the relevant numbers, including the most unique, rare, and extreme explosions in the Universe, such as Pair-Instability SNe (PISNe).

TEHLS will observe images of the same filter with a certain cadence: one natural way to do this is to observe the images at the two different roll angles with a time difference of at least 6 months, which would open up the discovery of slowly-evolving and/or high redshift transients, for example PISNe and superluminous (SLSNe) supernovae from Pop III stars. This would be especially effective if one of the filters is F213, but the currently proposed survey using F184 would still be revolutionary for IR transient science. While the 6+ months cadence probes the low-z IR Universe as well, it is not optimal since low-z transients evolve significantly faster than this time scale. We can remedy this by observing pairs of filters for a given roll angle, separated by weeks from the next pair of filters of the same roll angle. A single filter pair gives us color information for a given transient, while the two color pairs spread over a few weeks give us information about the color evolution as well as the overall light curve shape (e.g., rising or falling).

TEHLS alone will allow us to explore the IR nature of countless low-z transients, e.g. from Rubin or other wide-area time-domain surveys. However, the real strength of TEHLS is its potential as a discovery engine at both low- and high-z, with which we can trigger follow-up for the rarests and most exotic objects with HST, JWST, and ground-based telescopes like Gemini, Keck, and VLT! In our upcoming white paper, we show the current depth of HLS combined with its area is sufficient to color-select a unique sample of transient explosions that probe the high-redshift Universe. Such a survey would be successful if the current HLS were split into two epochs, but would be even more sensitive to high-z SNe if the F213 filter were added.
High Latitude Wide Area Survey stellar physics and stellar types, large scale structure of the universe Supernovae, Variable stars, Population III stars, Cosmology, Extragalactic Legacy And Deep Fields
Atsushi J. Nishizawa Gifu Shotoku Gakuen University Hironao Miyatake, Yuichi Harikane, Tsutomu T. Takeuchi, Tomomi Sunayama Masayuki Tanaka and HSC SSP survey team 25 deg^2 medium band filter survey with Subaru HSC Precise measurement of the redshifts of galaxies enables us to study various sciences including the clustering of large-scale structure, galaxy evolution with higher time resolution, or probing the large number of Lyman break galaxies at high redshifts z>4. In addition to this, the accurate redshift sample at faint magnitudes (down to imag ~ 26) is of great importance particularly for upcoming deep imaging surveys to calibrate the photometric redshift of the weak lensing sample. We propose to take 25 square degree sky, which is already observed by Subaru HSC SSP in 5 broad band filters, by using the 16 finner medium band filters. The suite of the HSC medium band filter dataset offers percent level accuracy of photometric redshift in scatter and outlier rate. The dataset requirements of the Roman imaging survey will be the same as those of HLWIS, with significant overlap with the Subaru SSP deep/ultra-deep fields at COSMOS, XMM-LSS, DEEP2-3 and ELAIS-N1 regions. High Latitude Wide Area Survey galaxies, large scale structure of the universe large-scale structure of the Universe, galaxy evolution, cosmology, galaxy clusters, gravitational lensing
Bahram Mobasher University of California, Riverside An Ultra-Deep, Wide-area Survey with the Roman Space Telescope: Exploring a New Parameter Space The combined field of view, resolution, wavelength coverage and sensitivity of the Roman will enable new science programs. The most direct precursor to Roman, the ESA-led Euclid satellite, has significantly lower angular resolution in the near-IR due to a combination of mirror aperture and pixel size as well as very broad filters. We propose to formulate a wide and ultra-deep survey that will best serve multiple science goals by extending our current studies to an entirely new parameter space. This requires supplementary multi-waveband deep observations over wide-areas from space- and ground-based observatories. Such data are needed to measure the photometric redshifts and physical parameters associated with galaxies. The on-going Hawaii-20 survey covers a total of 20 sq. deg area to deep levels with available photometry in optical bands as well as some of the deepest exposures by the Spitzer Space Telescope. Observations of the H20 by the Roman will provide the required data set to address a multitude of fundamental questions. Here, we elaborate on three programs that will be directly affected by such a survey.

(a). Search for Very High Redshift Massive Galaxies. The population of massive high-z galaxies is best studied by deep near-IR selected surveys. Given the small volume density of these galaxies, we need to cover a wide-area to obtain statistically large surveys. The aim here is to build the luminosity and mass function of these galaxies to high redshifts. A statistical study of this population will be the first of its kind and will impose strong constraints on the scenarios for the formation of galaxies. The galaxies can be selected through their Balmer Break features, with follow-up spectroscopy performed using PFS on Subaru to confirm their redshifts.

(b). Study of Proto-clusters and the Cosmic Web: We propose to identify the filamentary structures at different redshifts by performing wide and deep surveys optimized at near-IR wavelengths. This allows study of properties of different populations of galaxies in filaments, compare them with those in clusters and proto-clusters as well as in general fields. This will initiate a new study of the Intergalactic medium inside filaments. (c). Evolution and origin of morphological types of galaxies: This requires (1) high spatial resolution imaging survey of galaxies to measure their quantitative morphologies; (2). Deep infrared imaging data to allow rest-frame optical morphologies for high redshift galaxies; (3). statistically large sample of galaxies to constrain cosmic variance and to find significant number of galaxies with similar morphologies at each redshift. This will be used to study the origin of morphological types of galaxies (i.e. how the relative space densities of galaxies with different types change with look-back time) as well as the environment-morphology relation as a function of redshift.
High Latitude Wide Area Survey galaxies, the intergalactic medium and the circumgalactic medium, large scale structure of the universe High-redshift Galaxies, Extragalactic Legacy and Deep Fields, Large Scale Structure of the Universe, Galaxy Environments, Intergalactic Medium
Benne W. Holwerda University of Louisville Streams around edge-on Galaxies Early galaxy formation has presumably left a stellar halo of interaction and merger debris around the more massive galaxies. Thanks to the long dynamical timescales of stellar orbits in a galaxy's halo, much of the early mergers left coherent streams of stars. ESA's ARRAKIS mission and ground-based observations have discovered such streams in integrated light but this remains challenging as the streamers of stars left over from early galaxy formation are well below the night sky background. Much more secure is a halo measurement from resolved stars. The Hubble Space Telescope has the sensitivity to identify AGB and RGB stars in the haloes of nearby (<20Mpc) galaxies but not the field-of-view to map the substructure of the stellar halo without a prohibitive observational ask. This limitation is not one Roman faces.

With the wide field camera onboard Roman, one can map the stellar halo of an edge-on galaxy in one or two pointings. The perspective and continuous coverage allows one to identify streamers of RGB stars with similar colors (metallicity and therefore origin) and directly compare the fossil record of stellar streams to our understanding of galaxy formation.
High Latitude Wide Area Survey galaxies n/a
Bryan Holler STScI Richard Cosentino (STScI) Making the most of serendipitous solar system minor body observations The Wide Field Instrument (WFI) aboard the Roman Space Telescope will serendipitously acquire data of solar system small bodies during each Core Community Survey (CCS). Imaging of asteroids, comets, trans-Neptunian objects (TNOs), and even interstellar objects provide the astrometric and photometric information needed to constrain their orbits, rotational properties, and surface compositions, which allow for investigation into their origin and evolution, and by extension their respective populations and the solar system itself. We have identified an aspect in each of the High-Latitude Wide-Area (HLWA) and Galactic Bulge Time Domain (GBTD) surveys that would improve the study of solar system objects:

HLWA - Studies of the early dynamical evolution of the solar system indicate that the migration of Jupiter and Saturn produced a high-inclination population of asteroids that remained on those extreme orbits to the present-day. Comparison of photometry with WFI's F213 filter (similar to a Ks filter) to photometry from a continuum filter (e.g., F106), allows for broad-stroke spectro-photometric studies to infer the presence of hydrated minerals. Evaluation of the compositions of the high-inclination population would place constraints on the parent population of these objects. However, as currently defined, the HLWA survey does not include the F213 filter in its set. Inclusion of the F213 filter, at least for pointings within 40° of the ecliptic plane, would provide the information crucial for tracing the origins of the high-inclination asteroids and constraining details of the ancient migration of Jupiter and Saturn, a process that shaped the observed dynamical structure of the solar system.

GBTD - The rotation periods of asteroids can be indicative of their shapes and internal structure, or suggest the presence of an unresolved satellite. The YORP effect generally works to spin-up non-spherically symmetric objects, resulting in top-shaped bodies like Ryugu and Bennu, visited by the Hyabusa2 and OSIRIS-ReX spacecraft, respectively. The size of a body can be estimated based on its brightness and an expected rotation period due to the YORP effect calculated. Objects spinning slower than expected could be candidates for supporting unresolved satellites, which would work to despin the asteroid due to tidal interactions. Understanding asteroid binarity as a function of diameter down to small sizes would inform formation and collisional models. To this end, fine temporal sampling in the GBTD survey would enable the determination of high-precision rotation light curves for all asteroids in the FOV. The ecliptic crosses the galactic plane near the bulge, providing thousands of opportunities to compute the rotation periods of asteroids serendipitously moving through the patrol field.
High Latitude Wide Area Survey solar system astronomy Minor bodies, asteroids, compositions, rotation periods, orbits
Chevy suteja A world in support of act now UN The Global Goals High Latitude Wide Area Survey solar system astronomy, exoplanets and exoplanet formation, stellar physics and stellar types, stellar populations and the interstellar medium, galaxies, the intergalactic medium and the circumgalactic medium, supermassive black holes and active galaxies, large scale structure of the universe n/a
Craig Kolobow Florida Institute of Technology Eric Perlman Finding Galaxies Using Supernovae: A Roman Pathfinder Supernovae are some of the brightest events in the universe, making them visible at tremendous distances. However, their underlying host galaxies are not always detectable. Until fairly recently, only a few SNe have been discovered in such faint host galaxies as they have been well below the detection thresholds of their originating surveys. With the upcoming opening of the Rubin Observatory, we expect the number of undetected supernova hosts to greatly increase, as it conducts an all-sky survey with an 8.4m primary mirror, taking up to 200,000 images per year. It is difficult to accurately estimate the quantity of supernovae that Rubin will discover that will not clearly have an underlying host, but it is clear that follow-up observations with space telescopes will be needed to resolve them.

The Nancy Grace Roman Space Telescope is the ideal observatory for such follow-up, and the project aligns with Roman's General Astrophysics goals, utilizing the High Latitude Wide Area Survey to resolve the faint underlying hosts to previously "hostless" supernovae. This novel approach to galaxy detection offers a unique opportunity to discover otherwise undetectable galaxies. The main topic of my dissertation has been finding hostless supernovae in a pilot study using the ASASSN, PTF and other projects to find the supernovae and filter out those with obvious hosts, and follow-up imaging with APO, SOAR and Gemini. The objects found were almost entirely at z<0.1. The Nancy Grace Roman Space Telescope offers the opportunity to find many more such faint galaxies at considerably fainter magnitudes and at higher redshifts. Only through a variability survey (such as the High Latitude Wide Area Survey) and deep imaging can the faintest galaxies be observed throughout cosmic time, and without cause for deep imaging, these faint galaxies would remain undetected. Supernovae serve as a marker in otherwise empty regions of space; an indication that something underlying, yet invisible, served as the source of the supernova. We have a unique opportunity with Roman to solve these mysteries, and for the first time gain an appreciation of the structure and prevalence of faint mid-z galaxies.
High Latitude Wide Area Survey galaxies n/a
Dr. Mark Elowitz Network for Life Detection (NfoLD) Interstellar Object Search Survey The goal of this survey is to perform a deep (fainter than 22 magnitude) survey for any small objects that exhibit unusual motion, similar to the recently discovered 'Oumuamua. If any interstellar objects are discovered using the Roman Space Telescope, it is of interest to perform follow-up spectral observations using extremely large ground-based telescopes (e.g., E-ELT, US-ELT, GMT, ...) to determine the chemical/molecular composition of the object being studied. To investigate the possibility that one or more of these interstellar objects could be artificial in origin, follow-up spectral observations using these extremely large aperture telescopes is critical. Thus, using the Roman Space Telescope and Extremely Large Telescopes (to be operational late this decade) in synergy, the question as to the origin of objects similar to 'Oumuamua could be determined. High Latitude Wide Area Survey solar system astronomy ISO, 'Oumuamua, Interstellar, Spectroscopy, Survey retired genomics scientist Looking. For Genesis" the project's working hypothesis is that carbon based life forms present on earth were generated from organic molecule space along with heat , radiation and electrical energy such lightning free radicals

The project will use the data from JWST Nir spectrometer which generates an Infrared spectrum which is a molecular "finger print"of the molecules present in the target. The spectrum then can be searched in an IR data base to identify the molecule Subsequently ID biologic precursor and map their locations with in the target Carbon base life biomolecules

Phase one: ID target organic molecules

Project goal is to survey targets for molecule Identify pre-cursors to bio molecules in star and galaxies interstellar space
Looking. For Genesis" the project's working hypothesis is that carbon based life forms present on earth were generated from organic molecule space along with heat , radiation and electrical energy such lightning free radicals

The project will use the data from JWST Nir spectrometer which generates an Infrared spectrum which is a molecular "finger print"of the molecules present in the target. The spectrum then can be searched in an IR data base to identify the molecule Subsequently ID biologic precursor and map their locations with in the target Carbon base life biomolecules

Phase one: ID target organic molecules

Project goal is to survey targets for molecule Identify pre-cursors to bio molecules in star and galaxies interstellar space
High Latitude Wide Area Survey galaxies prebiotic molecules, pre nucleic acids,spark of life ,carbon based,
Francesca Annibali INAF - Astrophysics and Space Science Observatory of Bologna, Italy Understanding the hierarchical formation of dwarf galaxies through resolved-star studies of nearby systems with Roman Although dwarf galaxies are pivotal systems in the history of the Universe, many questions related to their formation and evolution in a Lambda CDM hierarchical merging paradigm remain poorly understood. Indeed, while studies of merging/accretion phenomena onto dwarf hosts have received little attention observationally so far (mostly because of the difficulty in detecting very faint satellites or merger signatures around them), such processes cannot be ignored, as interactions and accretions can strongly affect dwarf galaxies' morphology and kinematics, triggering the inflow of gas and the possible onset of starbursts. Reconstructing the past merging history of dwarf galaxies is also critical to test the predictions of LCDM cosmology down to the smallest galaxy scales.

Recent deep, wide-field ground-based surveys (e.g. the Solo survey [Higgs et al 2016], the MADCASH survey [Carlin et al. 2016], and the SSH survey [Annibali et al. 2020]) are discovering around nearby dwarfs an increasing number of low-surface brightness tidal features that provide direct evidence of the dwarfs' hierarchical merging assembling. Follow-up observations with HST are being pursued for a limited number of sufficiently nearby (D<10 Mpc) cases in order to infer the star formation history (SFH) of the host and satellites' remnants through resolved-star color-magnitude diagrams. These SFHs are a crucial ingredient to constrain (together with the galaxies' kinematical and morphological properties) N-body hydrodynamical simulations aimed at reconstructing the properties of the dwarf progenitors and their merging history. Unfortunately, these kind of studies are very time expensive, given the relatively small FoV of HST against the need to cover large regions around the dwarfs, limiting the number of systems that can in fact be studied.

A survey is thus proposed to observe with Roman a large sample of nearby dwarf galaxies to i) identify low surface brightness stellar streams based on stellar count over-densities, and ii) construct resolved-star color-magnitude diagrams that can be used to infer the galaxies' SFH over a very large area encompassing both the halo and possible stellar streams. Only the super resolution, sensitivity, and large field of view of Roman can allow to efficiently accomplish such a project.
High Latitude Wide Area Survey stellar populations and the interstellar medium, galaxies Dwarf galaxies; Galaxy mergers; Irregular galaxies; Star formation; Hertzsprung Russell diagram
Gregory Rudnick University of Kansas Nina Hatch, Michael Balogh, Mike Cooper, Benedetta Vulcani, Yannick Bahe, Benjamin Forrest, Gianluca Castignani, Gillian Wilson, Pascale Jablonka Roman-Cosmic Noon: A Legacy Spectroscopic Survey of Massive Field and Proto-cluster Galaxies at 2 < z < 3 Numerous studies over the last few decades have allowed us insights into how galaxy evolution depends on environment at z>1. Current evidence suggests that when the Universe was only a few billion years old, cluster galaxies were already more evolved than their field counterparts, but we do not know when these differences developed and whether they began prior to, or upon infall into clusters. Protoclusters are the place to answer these questions, as they provide a wide range of local densities over which to explore galaxies which will end up in clusters at lower z. However, environmental studies at earlier epochs have only scratched the surface of this question and are plagued by small and heterogenous protocluster samples with a high degree of variance between protoclusters. Key to addressing these topics are a large sample of protoclusters with robust spectroscopic membership and deep optical-NIR photometry. With the right observing strategy, the Nancy Grace Roman Space Telescope (NGRST) has the potential to revolutionize our understanding of the earliest dense regions in the Universe.

The protocluster discovery space of NGRST will be maximized with a survey that probes a large enough volume to find substantial numbers of protoclusters, that is deep enough to detect galaxies below L* regardless of their star formation history, and which has sufficiently deep spectroscopy and multi-band imaging to identify and characterize members. Our proposed survey is targeted at 2
High Latitude Wide Area Survey stellar populations and the interstellar medium, galaxies, the intergalactic medium and the circumgalactic medium, large scale structure of the universe Large-scale structure of the universe, Galaxy evolution, Galaxy environments, Galaxy formation, Quenched galaxies
Hironao Miyatake Nagoya University Tsutomu T. Takeuchi, Yuichi Harikane, Tomomi Sunayama Cosmology with large-scale structure measurements at z>~4 Large-scale structure (LSS) of the Universe is one of the powerful probes of cosmology, since LSS is the consequence of two competing effects; gravitational force by dark matter and cosmic acceleration by dark energy. To extract cosmological information from LSS, it is essential to map out the distribution of dark matter, which is not visible by light. Weak gravitational lensing (WL) enables us to measure the distribution of dark matter directly. Using WL measurements of LSS at z<~1, recent galaxy imaging surveys, such as Subaru Hyper Suprime-Cam (HSC), Dark Energy Survey (DES), and Kilo Degree Survey (KiDS), showed one of the cosmological parameters, the clumpiness of the LSS S_8, is smaller than that measured by anisotropies in cosmic microwave background (CMB). The tension is not yet significant, but the upcoming galaxy surveys including Nancy Grace Roman Space Telescope, will measure LSS at z<~2 with much more statistics to confirm the tension and explore a new model beyond the current standard model of cosmology.

Here, we propose another approach to explore the tension with LSS at high redshift (z>~4), which would provide us with additional information to constrain a model beyond the standard cosmological model. For this purpose, we use gravitational lensing of CMB caused by high-redshift Lyman-break galaxies (LBGs) selected by the drop-out technique and clustering of the LBGs. The proof-of-concent of this method is demonstrated in Miyatake et al. (PRL, 2022, 129, 061301), using LBGs at z~4 identified as the HSC g-dropputs. With Roman, to obtain robust cosmological constraints, we reduce contaminations from low-redshift galaxies using F213 observations in the overlapping region between Roman High Latitude Wide Area Survey and HSC. We also use HSC g-band and Roman F062 and F087 in the overlapping region to identify LBGs at z~5. In addition follow-up observations by PFS and medium-band observations by HSC enable us to reduce the contaminations in the sample. Combining with the results from WL measurement, we can obtain S_8 constraints across z~0 to z~5 seamlessly.
High Latitude Wide Area Survey large scale structure of the universe Cosmology, Dark energy, Large-scale structure of the universe, Gravitational lensing, Dark matter distribution
Ian Dell'Antonio Brown University The ICL and the dark matter and stellar halos of galaxies in nearby Clusters with the High Latitude Wide Area Survey Nearby (z<0.1) massive (M>10^14 Msun) galaxy clusters are not generally thought of as good targets for an extragalactic survey. However, their density on the sky is such that even a ~2000 square degree survey will cover O(100) such clusters as long as it is not designed specifically to avoid them. Thus, while there is perhaps a need for a targeted survey of these clusters, the HLWAS imaging can already make very important measurements in this regard. For the purpose of studying the galaxies, dark matter, and ICL in clusters, low-redshift clusters provide a unique laboratory, because the resolution with which the matter (both dark and baryonic) can be probed. The relationship between the ICL and the dark matter will be a sensitive probe of dark matter self-interactions.

The key will be producing an analysis of the HLWAS data which preserves low surface brightness flux over large scales (significant fractions of the Roman field), as well as provides calibrated shape measurements for much smaller background galaxies (for the weak lensing reconstructions). Because this measurement is somewhat different from the central goal of the HLWAS, care needs to be taken in imaging as well as data reduction to preserve this science case.
High Latitude Wide Area Survey the intergalactic medium and the circumgalactic medium, large scale structure of the universe galaxy clusters, intergalactic medium, galaxies, gravitational lensing
Ilsang Yoon National Radio Astronomy Observatory Roman will find the hidden binary supermassive black holes in the post-merger galaxies Identifying and studying the properties of binary supermassive black holes (SMBH) is a key astrophysical science goal of the coming decades. In future gravitational wave experiments, LISA will detect the formation and coalescence of binary SMBHs and the final merger event as LIGO does for stellar mass black holes. While the theoretical studies of the formation, evolution and dynamics of the binary SMBH have been well underway, the observational studies of binary SMBH do not yet give any useful constraint on the theoretical models and are not even close to a stage that we have a statistical sample for a range of dynamical configuration (e.g., separation and mass ratio).

Roman provides a 0.2" resolution deep NIR imaging with spectroscopic redshift for 100 times larger field of view than the HST. The Roman survey will discover many AGN host galaxies that are in late-stage merger where the two SMBHs are likely to be sitting in the obscured nucleus that is not visible in optical. The current ground-based NIR surveys do not have enough depth to confirm the post-merger signature and enough resolution to resolve the nuclear structure. With high-resolution radio observation complementary to the Roman NIR image, we can confirm and sample binary AGNs without observing bias. Roman will dramatically increase the sample size of binary SMBHs for a wide range of dynamical configuration and enable us to refine our understanding of the formation and evolution of SMBH, and even may forecast the GW event for the selective samples of binary SMBH.
High Latitude Wide Area Survey supermassive black holes and active galaxies AGN host galaxies, Supermassive black holes, Galaxy mergers
Ivanna Escala Princeton University Detailed Galaxy Assembly in the Local Volume with Roman Resolved Stellar Populations The Nancy Grace Roman Space Telescope (Roman) has the potential to transform our understanding of galaxy assembly by extending detailed studies of nearby systems to the edge of the Local Volume. A volume-limited survey of resolved stellar populations in the outskirts of nearby spiral and Magellanic type galaxies would be a natural extension of the capabilities of the High Latitude Wide Area Survey. This survey would address outstanding questions on stellar halo formation, the formation of low-mass galaxies, and the nature of dark matter that require larger samples of nearby galaxies to advance the field. Such questions include the relative contribution of in-situ vs. ex-situ halo formation channels, the dependence of halo properties on galaxy merger history, whether low-mass galaxies host halos and their origins, the properties of destroyed low-mass progenitor galaxies, constraints on the gravitational potential of host halos from tidal substructure, and the limit of small-scale structure formation in satellite galaxy systems.

Roman's unparalleled capacity for resolved wide-field imaging of red giant branch stars can carry out surveys with similar depth and scientific impact as the Pan-Andromeda Archaeological Survey (PAndAS) out to 10 Mpc within 1 hr of exposure time (and tiled with a single field). This could provide a homogeneous sample of Hubble Space Telescope quality observations for all ~160 spiral/Magellanic type galaxies within this volume with a survey footprint less than 45 sq deg. For nearby galaxies out to 4 Mpc, this exposure time would resolve stellar populations down to the horizontal branch, exceeding the depth of PAndAS. For each system, WFI imaging in two filters (such as F062 and F158) could provide a wide color baseline and a sufficiently large population of stars for the construction of deep color-magnitude diagrams. Such a survey with Roman could therefore enable the characterization of stellar substructure, the reconstruction of star formation history information, and spectroscopic follow-up with the next generation of ground-based telescopes throughout the Local Volume toward a comprehensive understanding of galaxy assembly.
High Latitude Wide Area Survey stellar populations and the interstellar medium, galaxies Galaxy stellar halos, Disk galaxies, Dwarf galaxies, Stellar populations, Galaxy formation
Jack Lissauer NASA Ames William J. Borucki, Daniel Huber, Jason Rowe, Steven Bryson Observing the Kepler Prime Field of View: Exoplanets, Stars & Galaxies The Roman FOV will have an area about 0.25%, so a typical pointing within the Kepler FOV would include ~500 Kepler target stars, ~400 of which were observed for most of Kepler's 4 years, and ~10 planet candidates. Observing a field for a week or more might provide significant useful information on stellar cycles. Roman's aperture is 6 times that of Kepler, so either one FOV could be used for the highest S/N observations or cycling could be done from 2 or 3 nearby FOVs, observing each once per 30 minutes to match Kepler's cadence and increase the area of the sky observed. Because of saturation of Roman's cameras, the most useful targets are likely to be those 14th magnitude and fainter, which make up the bulk of Kepler targets (although this is subject to change once the photometric accuracy of Roman on saturated targets has been measured; Kepler was able to do much more precise photometry on saturated targets than had been predicted prior to launch).

Pointings and timings could be selected primarily for individual target planets, either to validate and measure the radius of a candidate Earth or Venus analog, all of which have low S/N from Kepler, or to get TTVs for special small planets, e.g., to try to measure the masses of Kepler-62e and f (super-Earth size planets in the habitable zone), or to re-acquire the ephemeris of a long-period planet with TTVs for JWST follow-up. Stellar physics goals could play a significant role in FOV or filter selection. In addition to enhancing understanding of stellar cycles over a wide range of time scales, nice ancillary stellar science would be the measurement of oscillation and granulation amplitudes at IR wavelengths, which can then be compared to optical measurements from Kepler. Roman is also well-suited for asteroseismology of evolved stars: Or some FOVs could be designed to look at areas in the Kepler FOV that are especially useful for deep exposures of galaxies or for a substantial number of target stars of different types to obtain better time series photometric measurements or precise color photometry to combine with Kepler's long time series, or any combination of goals such as these, since any pointing in the Kepler FOV will have multiple benefits, the magnitude of each depending on the specifics of the pointing and choice of filter(s).
High Latitude Wide Area Survey exoplanets and exoplanet formation, stellar physics and stellar types Exoplanet transits, stellar cycles
Jenny Greene Princeton University Rachel Bezanson, K.G. Lee, John Silverman, Masami Ouchi, Taddy Kodama, Tim Heckman for the PFS Galaxy Evolution Working Group Galaxy Evolution with the High Latitude Survey and the Prime Focus Spectrograph At the lowest redshifts (0.7L_*, allowing a wide range of studies including the environmental dependence of galaxy quenching and evolution in the mass-metallicity relation. We will also perform an IGM tomography survey of 2
We therefore propose that the RST High Latitude Survey include the fields being targeted by PFS-GE, which is a subset of the ~30 deg^2 Hyper-Suprime Camera Deep fields (XMM-LSS, eCOSMOS, Elais\-NI, Deep2-3). In addition to the 12.5 deg^2 of PFS spectroscopy, HSC-Deep has imaging in 5 broad bands (grizY) reaching depths of 27 mag [AB mags throughout] over an area of 30 deg^2 with unmatched image quality (0.6 arcsec), along with three narrow bands. There is deep U-band data over the full area [to 27~mag, with 350h of CFHT time], decent J-band to J~23~mag, and deep Spitzer IRAC coverage (depth 23.1; PI: Lacy and Sajina). Such wide wavelength coverage will prove helpful in calibrating and maximally using the HLS data for galaxy evolution science.

The combination of the PFS spectra and the RST imaging will be incredibly powerful. In the same galaxies we can study morphology, mass, star-formation rate, chemistry, and even outflow properties. A primary, driving goal of the PFS Galaxy Evolution survey is to spectroscopically map the backbone of the evolving cosmic web. Combining this map with photometric information from HSC and RST will provide the highest fidelity, detailed 3D distribution of galaxies at Cosmic Noon and beyond, thus enabling unparalleled tests of the role of large scale (PFS + HSC) and small scale (HSC + RST) environment in driving galaxy evolution. Secondarily, we may be able to calibrate the blended Halpha+[NII] lines in the RST grism spectra with high-resolution PFS spectra at 0.7
High Latitude Wide Area Survey galaxies, supermassive black holes and active galaxies, large scale structure of the universe Dark matter distribution, Galaxy groups, Reionization, Quenched galaxies, AGN host galaxies
John Bally Astrophysical and Planetary Sciences, University of Colorado, Boulder Jets, Outflows, and Shocks in from Forming & Dying Stars in The Milky Way I propose a survey of the Galactic Plane and some nearby off-plane star-forming molecular clouds with Roman. A survey of the fields covered by the Spitzer near-IR (GLIMPSE), mid-IR (MIPSGAL), and Herschel far-IR (Hi-GAL) surveys with Roman's ~0.1 arc-second resolution will provide a wealth of information on Galactic stellar populations, star-formation, stellar death, the interstellar medium (ISM), and the feedback processes that regulate the ISM's state. A re-observation in a decade after the first survey will measure Galactic stellar proper motions

Most astrophysical systems which rotate, accrete, and have magnetic fields power jets and bipolar outflows. Examples include protostars, dying stars, symbiotic binary systems, neutron stars, and black holes surrounded by accretion disks. Accretion-powered jets and outflows share many similarities despite orders of magnitude differences in mass and size scales. Their morphologies tend to be similar: highly collimated, bipolar beams near the source which break into chains of bow shocks farther out. Outflow speeds tend to be a few times the equivalent circular orbit speed where the outflow is launched - a few hundred km/s for protostars and near the speed of light for black holes and neutron stars.

Most young stellar objects (YSOs) and many post-main-sequence stars drive jets and bipolar outflows while they accrete. These objects constitute the nearest class of accretion-powered jets and outflows. Due to their proximity, structural changes and proper motions can be measured on time-scales ranging from weeks to decades. Studies of these systems provide nearby laboratories for the investigation of all classes of accretion powered outflow systems.

Roman's broad-band filters can identify extended nebulosity produced by shocks, ionized nebulae powered by young massive stars, supernova remnants and stellar wind bubbles, enable powered by recently collapsed stellar cores (planetary nebulae). Specifically, the emission lines of hydrogen (1.87 um Paschen-alpha, etc.) trace visually obscured ionized nebulae and recombining plasma behind shocks. Shocks are particularly bright in the 1.644 um line of [FeII] when propagating into atomic media, and the 2.12 um line of molecular hydrogen when propagating into molecular media. These extended nebulosities can be identified by morphology and distinguished from scattered or continuum emission (e.g, from unresolved stars) by image arithmetic. For example, the 1.87 um HI and 2.12 um molecular hydrogen line emission regions can be identified by differencing the F184 and F213 filter images. This works because the two emission lines trace very different environments and are usually spatially separated.

Visual to near-infrared, wide-field surveys with Roman of the Galactic Plane and nearby low-Galactic-latitude star-forming clouds such as Taurus, Orion, and Perseus can be used to identify outflows from forming and dying stars.

The goals of Galactic plane surveys are:

- Identify large populations of young stellar objects, protostellar outflows, HII regions, stellar wind-bubbles, proto-planetary and planetary nebulae.

- Observe the Hi-Gal and Spitzer fields with sub-arcsecond resolution in all Roman filters: The Galactic plane plus off-plane clouds require about 1,000 square degrees. 360 x 2 degrees along the Galactic plane, and about 280 square degree off the plane which contains star-forming clouds such as Orion , Taurus, and Perseus.

- Special emphasis will be to study the Central Molecular Zone of the Milky Way which comprises the central ~500 pc of the Galaxy, and serves as a nearby analog of star-birth in high-pressure environments thought to occur in the high-redshift Universe.

- A repeat of the survey in the near-IR filters about a decade after the initial observations will reveal Galactic stellar proper motions not observable with Gaia.

Roman Galactic surveys provide the "ground-truth" for interpreting the physics of star-formation, stellar death, and feedback which regulates the physical and chemical states of galactic interstellar media.

Note: Narrow-band filters tuned to the 1.64 um, 1.87 um, and 2.12 um emission lines would be extremely useful additions to Roman's complement of broad-band filters. These filters would enable observations of brighter stars, and would improve Roman's ability to study the ISM. These filters wold also be useful for identification of high-redshift emission-line galaxies at specific redshifts.
High Latitude Wide Area Survey stellar physics and stellar types, stellar populations and the interstellar medium astrometry, HII regions, interstellar medium, stellar jets, protostars
John Blakeslee NOIRLab (National Optical-Infrared Astronomy Research Laboratory) Uniform Galaxy Distances within 100 Mpc for Astrophysics and Cosmology Reliable extragalactic distances are essential for converting the observed properties of galaxies, clusters, black holes, and cosmic explosions into physical quantities. They have been the key to revealing the dominance of dark matter on large scales and the presence of dark energy. Yet, except for very nearby, resolved systems, they are notoriously difficult to estimate, and "factor-of-two problems" are not uncommon. To take one example, the diffuse galaxy NGC 1052-DF2 was claimed by van Dokkum et al (2018 Nature, 555, 629) to be devoid of dark matter, based on a distance of 20 Mpc from surface brightness fluctuations (SBF). A subsequent study (Trujillo et al. 2019, MNRAS, 486, 1192) argued that the galaxy had normal dark matter content based on a distance of 13 Mpc, estimated mainly from the globular clusters. Thus, the interpretation was wildly different, depending on the distance. A subsequent measurement of the tip of the red giant branch (TRGB) yielded d = 22.1 +/- 1.2 Mpc (Shen et al. 2021, ApJ, 914, L12), consistent with the best earlier SBF distance of d = 20.4 +/- 2.0 Mpc (Blakeslee & Cantiello 2018 RNAAS, 2, 146). The remarkable thing is that the TRGB distance was based on 40 orbits of HST/ACS data, while the SBF distance was based on a single orbit. Unlike other precision distance indicators (Cepheids, TRGB, SN Ia, masers), the SBF methods requires only a single epoch with modest depth. As a result, it has been widely used with HST to study the 3D structure of nearby galaxy clusters (Blakeslee et al. 2009; Cantiello et al. 2018a), convert the observed "shadow" of the M87 supermassive black hole into a physical size (and thus a mass; EHT Collaboration 2019), and to measure the most precise distance to the host galaxy of GW170817 (Cantiello et al. 2018b), the first gravitational wave source with an optical counterpart. The method has also produced a competitive value of H0=73.3+/-2.5 based on 63 galaxies observed with HST WFC3/IR out to 100 Mpc (Blakeslee et al. 2021).

However, with HST, the SBF measurements have been one orbit at a time. With Roman, we have the opportunity to measure uniformly high-quality distances to many thousands of galaxies out to at least 100 Mpc, and potentially twice that far, depending on depth and wavelength selection. This will enable accurate measurements of dark matter content, physical sizes, luminosities, black hole mass, etc, as well as an independent value of H0 with negligible statistical uncertainty. This project would use data from the High Latitude Wide Area Survey; for best results, the survey should maximize the area covered (at least 4000 sqr deg; ideally closer to a quarter of the sky), in a band optimized for the method (e.g., Y106, or possibly J129). The resulting data set, including the measured distances, will be a phenomenal resource for galactic structure, near-field cosmology, and other areas.
High Latitude Wide Area Survey galaxies, large scale structure of the universe Galaxy environments, Galaxy spheroids, Large-scale structure of the universe, Dark matter distribution, Cosmological parameters
Jordan Mirocha JPL/Caltech Paul La Plante, Adelie Gorce, Adam Lidz, Aaron Parsons, Steve Furlanetto, Andrei Mesinger Cross-correlations between high redshift 21-cm measurements and the Roman HLS Cross-correlations between high redshift galaxy samples and 21-cm maps from low-frequency radio observatories (e.g., the Hydrogen Epoch of Reionization Array, the Square Kilometer Array; HERA, SKA) have long been recognized as a powerful way to study early galaxies and the Epoch of Reionization (EoR). For example, the 'de-correlation scale' between the galaxy and 21-cm fields indicates the typical size of ionized regions, while the overall power is sensitive to the global ionized fraction, the temperature of the intergalactic medium, and the typical masses of halos hosting high-z galaxies. Cross-correlations also provide a vital check on efforts to detect the 21-cm power spectrum, which are complicated by bright foregrounds and instrumental systematics.

In a recent paper (La Plante et al., 2023; astro-ph/2205.09770), we showed that the prospects for a cross-correlation detection using galaxies from the Roman High-Latitude Survey (HLS) and 21-cm measurements from HERA are strong. In the most optimistic scenarios, our predictions suggest a more than 10-sigma detection is possible, in which case one would have enough signal to constrain the cross-power in multiple redshift and/or k-mode bins and begin to constrain the sizes of ionized bubbles and the timeline of reionization. However, some pessimistic scenarios, e.g., if the fraction of galaxies with Lyman-alpha detections is much lower than expected, we might expect only a marginal detection. We showed that going one magnitude deeper over 100 deg^2 of the HLS (HERA has ~500 deg^2 of overlap with the nominal survey centered at a declination of -30 degrees) would enable a secure detection in every scenario we explored, and so guarantee constraints in multiple k and z bins. A ~50% increase in the depth of the spectroscopic survey (to ~5 x 10^-18 erg s^-1 cm^-2 Hz^-1 sr^-1) would help ensure Lyman-\alpha detections as well. This additional depth would undoubtedly be beneficial also to future cross-correlation efforts with the SKA, and high-z galaxy evolution studies in general.
High Latitude Wide Area Survey galaxies, the intergalactic medium and the circumgalactic medium, large scale structure of the universe galaxy formation, high-redshift galxies, intergalactic medium, reionization
Joshua Schlieder NASA GSFC Brown Dwarf and Free-Floating Planetary Mass Object Science in Roman's High Latitude Imaging and Spectroscopy Survey Sub-stellar sources are a natural outcome of star formation process. These brown dwarf and free-floating planetary mass objects have masses in the range of ~5 < MJup < 80 and effective temperatures 200 K < Teff < 2000 K. This mass and temperature range spans an order of magnitude and leads to very different interior, atmospheric, and spectral properties across the sub-stellar regime. This makes them prime laboratories for understanding the very low-mass end of the IMF, binary populations, and the transition between brown dwarfs and planets.

Roman's High Latitude Imaging and Spectroscopy Survey (HLISS) will provide a wealth of data on this sub-stellar population. The deep multi-band IR imaging and grism spectroscopy will allow for internal calibration of photometric color selection and direct characterization through spectra and model fitting. The HLISS has the potential to increase the known population of brown dwarfs and free-floating planets by 10-fold and provide for the first time a complete census of these objects through a slice in the galactic disk. Roman's high precision astrometry will also allow for deep study of their kinematics and their power as tracers of evolution and structure in the galaxy. The sub-stellar science potential of the HLISS could be expanded by the inclusion of deeper grism observations and using the K-band filter.
High Latitude Wide Area Survey exoplanets and exoplanet formation, stellar physics and stellar types, stellar populations and the interstellar medium brown dwarf stars, Free floating planets
Kathleen Kraemer Boston College Martha Boyer (STScI) Steve Goldman (STScI) Caroline Huang (Harvard-Smithsonian CfA) Atefeh Javadi (IPM) Abby Lee (Univ. Chicago) Noriyuki Matsunaga (Univ. Tokyo) Iain McDonald (Univ. Manchester) Nami Mowlavi (Univ. Geneva) Peter Scicluna (ESO) Greg Sloan (STScI) Sundar Srinivasan (UNAM) Michelle Trabucchi (Univ. Geneva) Alfonso Trejo (UNAM) Jacco van Loon (Keele Univ.) Diego Alejandro Vasquez (UNAM) Patricia Whitelock (SAAO) Setting the Stage for Improving the Distance Ladder with Roman Core Community Surveys Background: The upcoming Nancy Grace Roman mission offers an unprecedented opportunity to improve the cosmic distance ladder, and the Core Community Surveys (CCS), if properly designed, can play a key role in this endeavor. The use of long period variable stars (LPVs) as standard candles can extend our reach beyond the limits achievable with Cepheids, since the intrinsic luminosities of the LPVs are significantly higher and hence can be detected at larger distances. Recent work has calibrated the "J-AGB" method using J-band photometry and Gaia distances for Galactic carbon stars (Lee et al. 2021, 2022), and Hubble near-IR photometry of oxygen-rich Miras in supernova host galaxies (Huang, Riess, et al. 2018, 2020). A significant limit of the method to date, though, is the small number of galaxies to which it has been applied, largely due to limits of current facilities (fields-of-view, no/limited near-IR bands, sensitivity, insufficient revisit rate, etc.).

Proposed science investigation: All three of the planned Core Community Surveys have the potential to impact this field. The most important will be the High Latitude Wide Area Survey with its large area, 2-year survey using the Y106, J129, H158, F184 filters + Grism. In terms of this call for science concepts and the CCS design, the key is to maximize the number of galaxies in the survey regions for which LPVs can be detected. These multi-band data will enable us to identify and characterize the evolved star populations in these galaxies. Thus, as the survey is designed in detail, the exact locations of the pointing centers should be optimized to include these galaxies. As most of the science cases will be using data from well within the survey footprint, a small pointing adjustment to include more of our target galaxies should be transparent to other users in the community but could improve our studies significantly.
High Latitude Wide Area Survey stellar physics and stellar types, stellar populations and the interstellar medium, galaxies evolved stars, stellar distance, variable stars, infrared photometry, stellar populations
Keith Bechtol University of Wisconsin-Madison Peter Ferguson, Nushkia Chamba, Alex Drlica-Wagner, Jeffrey L. Carlin, Ethan O. Nadler, Andrew Pace, Burcin Mutlu-Pakdil, Nora Shipp, Will Clarkson, Annika Peter, Jennifer Sobeck, Kristen Dage Coordinating Roman and Rubin Surveys for Cosmic Probes of Dark Matter We are interested in coordination between the Nancy Grace Roman Space Telescope and the Vera C. Rubin Observatory to enhance cosmic probes of dark matter. Astrophysical observations probe the physics of dark matter through its impact on structure formation throughout cosmic history. Fundamental properties of dark matter - e.g., particle mass, self-interaction cross section, coupling to the Standard Model, and time evolution - can imprint themselves on the macroscopic distribution of dark matter in a detectable manner by modifying the abundance, density profiles, and spatial distribution of dark matter halos. Astrophysical observations offer unique sensitivity to a wide range of dark matter particle models (including particle candidates that interact only through gravity) and are highly complementary to terrestrial experiments and indirect dark matter searches. Additionally, measurements of the dark matter distribution across a wide range of physical length scales can be used to constrain the physics of the early Universe, including inflation as well as non-standard cosmologies, e.g., with early matter domination.

In the coming years, Roman-Rubin coordination could enhance studies of dark matter halos that are below the minimum mass threshold to host stellar populations. This halo mass range below 10^8 solar masses is the next observational frontier. These halos offer unique advantages to constrain the microphysical properties of dark matter because their evolution is less affected by complicated baryonic physics and because many "non-minimal" dark matter properties leave the most conspicuous signatures on low-mass halos. We highlight two example opportunities for Roman-Rubin coordination.

(1) The combination of optical (Rubin) + space-based near-IR (Roman) imaging would allow efficient star-galaxy separation to enable detailed studies of the Milky Way stellar halo and ultra-faint galaxies several Mpc beyond the Milky Way virial radius (taking full advantage of unprecedented depth of both surveys). We would be able to conduct a detailed census of the low-mass galaxies throughout the Local Volume to firmly establish the threshold halo mass for galaxy formation (likely around 10^8 solar masses), and search for density perturbations in stellar streams caused by interactions with even lower-mass dark matter halos (10^6 - 10^8 solar masses).

(2) We could use the combination of Roman-Rubin to identify thousands of galaxy-scale strong lenses (taking advantage of optical to near-IR colors), and utilize the space-based angular resolution of Roman to select optimal candidates for follow-up observations with other facilities. There are two ways to use strong lensing to study low-mass dark matter halos within the main deflector and along the line of sight: flux-ratio anomalies and gravitational imaging (distortion of arcs). In combination with dedicated follow-up observations (e.g., JWST, ELTs), we would aim to access properties of dark matter halos in the mass range 10^6 to 10^7 solar masses.

Both of the techniques above benefit from large sky areas covered with both Roman and Rubin. It would be optimal to have a wide-area survey with Roman covering the majority of the LSST footprint in at least one band. This approach would combine multiband deep optical photometry from LSST with space-based resolution from Roman. For the star-galaxy separation use case, joint pixel processing, or at least forced photometry, would be important to ensure consistent object detection and photometry between the two datasets, and we need robust color measurements to take full advantage of the separation of galaxy and stellar loci in optical + near-IR color space. We note that similar survey concepts have been considered for other cosmology science cases, e.g., for weak gravitational lensing and galaxy clustering probes of dark energy
High Latitude Wide Area Survey stellar populations and the interstellar medium, galaxies, large scale structure of the universe Galaxies:Galaxy dark matter halos, Galaxies:Dwarf galaxies, Large Scale Structure of the Universe:Dark matter distribution, Large Scale Structure of the Universe:Gravitational lensing, Stellar Populations (and the ISM):Dwarf galaxies
Kohei Ichikawa Tohoku University Revealing high-z radio universe through wide-IR eyes Recent wide-area radio surveys such as VLASS covers the GHz radio sky down to Dec > -40 deg. After the cross-matching with Subaru/HSC SSP wide-area optical survey covering ~10^3 deg^2, our team has found interesting sources whose optical counterpart is completely dark down to i_AB ~ 26 mag and we call them HSC-dark radio sources. We have recently conducted the NIR counterpart search in the HSC SSP deep field and some of them show an emergence of the emission in NIR. Assuming that Lyman break causes the darkness in optical, and considering that the strong radio emission in VLASS secures that the sources are radio AGN (or Quasars), they are prominent candidates of high-z (z>7) radio quasars which have not been discovered before (Fitriana et al. in prep.), and there are sources whose NIR emissions are missing, or dark down to K_AB ~ 24 mag. The high latitude Roman survey will provide the first NIR detections of such interesting sources bright in the radio sky and will also provide the most distant radio quasar candidates at z>7. This study will be realized thanks to Roman's very deep and wide NIR eyes. High Latitude Wide Area Survey supermassive black holes and active galaxies Quasars, Radio cores, High-luminosity active galactic nuclei
Kristen Dage McGill University Christopher Usher, (Stockholm University, Sweden); Jennifer Sobeck, (CFHT, USA); Ana Chies Santos (UFRGS, Brazil); Robert Szabo (Konkoly Observatory, Hungary); Marta Reina-Campos (McMaster University, Canada); Léo Girardi (INAF-Padova, Italy); Vincenzo Ripepi (INAF-Capodimonte, Italy); Marcella Di Criscienzo (INAF-Rome, Italy); Ata Sarajedini (Florida Atlantic University, USA); Will Clarkson (University of Michigan-Dearborn, USA); Peregrine McGehee (SLAC, USA), Katherine Rhode (Indiana University, USA) Extragalactic Star Cluster Science with the Nancy Grace Roman Space Telescope and the Vera C. Rubin Observatory Star clusters provide a window onto a wide range of astrophysical processes and hold the answers to key questions regarding how stars form, evolve, and die, as well as how galaxies form and evolve. Moreover, observational and theoretical studies have demonstrated that globular clusters are effective probes of the shape and structure of their host galaxies, including the galaxies' dark matter halos. Synergistic observations from the Nancy Grace Roman Space Telescope's High Latitude Wide Area Survey and the Vera C. Rubin Observatory's Legacy Survey of Space and Time will allow for an entirely new characterization of extragalactic star clusters, reaching the turnover of the cluster luminosity function at distances out to 100 Mpc. Combining data from the two surveys will enable us to analyze stellar populations across the broadest wavelength range yet achieved, and Roman's higher spatial resolution will allow us to estimate the sizes of globular clusters in external galaxies with a wide range of properties and environments. Measurements in blue optical filters from Rubin are crucial for globular cluster science, because near-infrared photometry alone is not sufficient to break the age-metallicity and age-extinction degeneracies. The latter is a fundamental issue in studies of stellar populations in star-forming galaxies.

The core synergies between the two facilities will drastically improve our understanding of stellar populations and host galaxy assembly, but will also help us understand the populations of exotic stellar objects found within globular clusters (and by extension, the progenitor sources of gravitational wave events). Observing extragalactic globular clusters with Roman alone will allow us to measure globular cluster metallicities, but breaking the age/metallicity degeneracy requires data from both Rubin and Roman. Breaking this well-known degeneracy will make us more effective at selecting and studying extragalactic star clusters and will represent a major step forward in our understanding of the assembly history of galaxies and their dark matter content. Roman's excellent spatial resolution will provide information on the sizes and structures of the globular clusters; this information, when paired with age/metallicity measurements, can be combined with multiwavelength observations to securely link globular cluster properties to stellar exotica, including the progenitors of merging black hole black-hole binaries.
High Latitude Wide Area Survey stellar physics and stellar types, stellar populations and the interstellar medium, galaxies globular clusters, stellar populations, black holes, X-ray binaries
Lan Wang National Astronomical Observatories, Chinese Academy of Sciences The relation between galactic bulge formation and galaxy merging Classical bulge and pseudo bulge differ statistically in color, profile, SFR and many other properties. Galaxy merging has been proposed to play a role in the formation of galactic bulges, especially for classical bulges, but the robustness and details have not been settled. For SDSS galaxies in the local Universe, Wang et al. 2019 found that pseudo bulge galaxies have more close neighbors (<100kpc) than classical bulge galaxies, which implies strong connections between pseudo bulges and galaxy-galaxy interactions. Due to the limited image resolution of SDSS, the result needs to be verified and deserves further investigation.

With the help of Roman (High Latitude Wide Area Survey), we aim to select large samples of galaxies with different types of bulges, and study the statistical differences in the properties of bulges, bulge galaxies, and their close neighbors, to study the relation between bulge formation and galaxy merging/interaction in detail. Roman provides high image resolution which is crucial in identifying robustly the types of galactic bulges. The wide area of the survey enables to get a large enough sample to do statistics. While the survey can observe galaxies up to redshift around 3, galactic bulges at different epochs can be studied. In particular, at redshift of around 2, the cosmic galaxy merging rate is high, and more galaxies undergoing mergers can be observed. If merger/interaction is indeed closely related to the formation of bulges, the investigation of galaxies at different stages of merger/interaction can provide more details.
High Latitude Wide Area Survey galaxies Galaxy bulges, Galaxy mergers, Galaxy formation, Galaxy evolution
Luigi R. BEDIN INAF OAPD if I can I would be happy to be co-author Stellar populations, close-by stellar objects, stellar systems I would like to see NRST to have during a multi-years campaign to cover as much as possible the entire sky. possibly at least two times in two - thee fiters. That would enable to extend Gaia catalog to magnitude V~27, enabling several scientific application and making Roman Telescope a real Treasury mission lasting many generations. High Latitude Wide Area Survey solar system astronomy, stellar populations and the interstellar medium astrometry - photometry - stellar populations
Mark Lacy NRAO Kristina Nyland (NRL), Dillon Dong (NRAO) Synergies between Roman and the VLA Sky Survey The VLA Sky Survey (VLASS), a 3-epoch survey of the radio sky at 2-4GHz with a 32 month cadence is currently being carried out. With a resolution of 2.5-arcsec, it is the highest resolution large-area radio survey to date (and likely to remain so for the foreseeable future), making it particularly valuable for associating radio sources with host galaxies detected by surveys with the Nancy Grace Roman Space Telescope. VLASS covers all the sky north of declination -40 degrees, so for overlap with VLASS surveys with Roman will need to avoid lower declinations. Science cases using a combination of Roman and VLASS include:

(1) the characterization of radio source host galaxies in the high latitude survey. Radio source host galaxies are unique laboratories for studying the effects of AGN jet feedback on the ISM and CGM of galaxies. A study of a large sample of these will allow investigation of the merger fraction of radio AGN host galaxies and the frequency of dual AGN extending down to radio luminosities close to the radio-loud/radio-quiet boundary. VLASS will have a source density of ~100 objects per square degree, most of which are AGN, so in a 2000 deg^2 survey with Roman we expect ~200,000 host galaxies ranging in redshift from 0 to ~5. The high redshift host galaxies, which are frequently dusty, will benefit from the near-infrared coverage of Roman. The well-established K-z relation for radio source hosts suggests that radio source hosts even out to z~5, with K_AB~23, will be detectable in ~2min of exposure. Although the F213 filter is less sensitive, these objects are typically very red, so including the F213 filter in the high latitude survey, either in addition to F184, or as a replacement for that or one of the other filters would be beneficial for this science.

(2) imaging of the hosts of radio transients. Although VLASS is currently scheduled to complete its survey in 2024, before Roman launches, we expect to have identified several thousand radio transients in the data. Even in a ~2000 deg^2 survey with Roman we would expect ~100 transient hosts, mostly supernova host galaxies and the hosts of Tidal Disruption Events (TDEs). The high resolution of Roman will allow us to distinguish between whether the event was a nuclear transient such as a TDE or AGN flare or an off-nuclear even such as a supernova. Further transient science could be performed in conjunction with DSA-2000, a planned dedicated survey radio telescope situated in Owens Valley, CA. This opens up the possibility of joint optical/infrared and radio-based transient searches on a timeline similar to Roman.
High Latitude Wide Area Survey supermassive black holes and active galaxies AGN host galaxies, Galaxy jets, Supernovae, Quasars, Galaxy evolution
Massimo Ricotti University of Maryland Detecting "Ghostly" Stellar Halos in Nearby Dwarf Galaxies Ghostly stellar haloes are extended haloes of stars composed solely of debris of pre-reionization fossil galaxies and they should exist in dwarf galaxies with total masses <10^10 Msun. Fossil galaxies are even smaller mass dwarf galaxies that stopped forming stars after the epoch of reionization and have been identified in the Local Group as the ultra-faint (UF) dwarf satellites. Both UF dwarf galaxies and Ghostly halos can be used to constrain star formation in the smallest galactic building blocks that formed before the epoch of reionization, Understanding star formation in these small mass halos is important to understand the epoch of reionization, PopulationIII star formation and even constrain the nature of dark matter.

These stellar halos, if they exist, are predicted to have extremely low surface brightness but they can be detected in nearby dwarf galaxies by star counts (typically looking for RG branch stars) and tentative detections have been reported for Leo T, Leo A, IC 10, WLM, IC 1613 and NGC 6822. The large field of view of the Roman Space Telescope and its sensitivity are uniquely suited to detect these halos to their further extent with few telescope pointings: the radii of these halos can extend to over 40 arcmin from the central galaxy and the outer parts are most interesting to constrain star formation in the smallest galaxies as they deposit most of their stars further out. Stars belonging to Ghostly halos are selected against foreground M-dwarf stars in the Milky Way halo using color magnitude diagrams (eg, I vs V-I). Special filters that are sensitive to metallicity (eg, SkyMapper intermediate-band filter covering the prominent Ca II K feature at 3933.7 A) can help separating low-metallicity Ghostly halo stars from foreground M-dwarfs.
High Latitude Wide Area Survey stellar populations and the interstellar medium, galaxies, the intergalactic medium and the circumgalactic medium Galaxy stellar halos, High-redshift galaxies
Matthew De Furio University of Michigan - Ann Arbor Michael R. Meyer Pushing the Limits of Star Formation Theory: An in Depth Exploration of Large Star-forming Regions Star forming regions contain clues to uncovering the details of the star formation process. They have a wide variety of environmental properties, ranging from very low density associations with few stars to very high density, bound clusters with hundreds of thousands of stars. Past studies have identified no difference between the distribution of masses, the initial mass function (IMF), within various stellar populations, although this remains unclear for sub-stellar objects down to the limit of turbulent fragmentation, ~ Jupiter mass scales (Bastian et al. 2010). Importantly, environmental differences have been identified within the stellar multiple populations of Taurus (a low-density association) and the Orion Nebula Cluster (a high-density cluster), likely due to dynamical encounters during states of very high density (De Furio et al. 2022). With the Nancy Grace Roman Space Telescope (Roman), we can probe star formation properties within a wide variety or star-forming environments in order to: a) define the stellar and sub-stellar membership unattainable from the ground or other space-based telescopes, b) define the limit of turbulent fragmentation, the very low mass end of the IMF, and identify any potential environmental impacts (e.g. metallicity, presence of OB stars), and c) characterize the multiple populations down to planetary mass primaries and angular resolutions of ~ 100 milli-arcseconds (mas).

Current work with the James Webb Space Telescope (JWST) is designed to explore the very low mass end of the IMF in dense embedded clusters. While no other telescope can match the sensitivity of JWST in the infrared, the field of view of NIRCam is nearly 100x smaller than that of the wide-field instrument on Roman. On the other hand, ground-based telescopes are not sensitive enough to the low-mass sub-stellar population, particularly when extincted, and cannot attain high angular resolution over a large field of view. Space-based survey telescopes (like Gaia) are also not sensitive to the faint sub-stellar members of star-forming regions and suffer from extinction in the visible. Roman is crucial to observing regions on large angular scales like OB associations, those with thousands of stars and potentially the most common location of star formation, in order to explore the fundamental features of the star formation process. Roman is the only observatory that can be used to characterize the sub-stellar content across large scale star-forming regions in the near infrared and have the efficiency to explore multiplicity down to separations of 100 mas across entire star-forming regions. With the observations of dozens of star-forming regions, across 0.5-2.3µm, Roman will serve as the gold-standard in star formation astrophysics, complementary to work done by JWST in deeply embedded clusters, and provide a large database for future archival research in areas like the formation and evolution of protoplanetary disks.
High Latitude Wide Area Survey stellar physics and stellar types, stellar populations and the interstellar medium Star formation, Star clusters, Brown dwarf stars, Binary stars / Trinary stars, Pre-main sequence stars
Mireia Montes Instituto de Astrofísica de Canarias (IAC) on behalf of the LSST Low Surface Brightness Working Group A Roman Deep Field to unveil the faint Universe. The low surface brightness (LSB) Universe is the last frontier for our understanding of structure formation in the Universe. While astronomical sources with the lowest stellar densities have remained largely undetected in previous wide-field surveys, the next generation of deep surveys promises to deliver transformational insights into our knowledge of star formation in the lowest mass regime, the hierarchical assembly of galaxies and clusters of galaxies, and constraints on the nature of dark matter. Roman is especially suited to study the LSB Universe thanks to its 1) large field-of-view providing the large areas of the sky necessary to explore the LSB Universe statistically, and 2) spatial resolution, minimizing blending of sources and allowing a pristine characterization of LSB structures, including the identification of globular clusters in nearby LSB galaxies.

An ultra-deep field survey (5 sigma point source depths of mAB~30) will represent a major leap forward from existing ultra-deep surveys by increasing the area by a factor of 100. It is imperative to reach these depths in order to reveal the faintest sources in the sky, such as stellar haloes around galaxies and inside galaxy clusters at large radii. Furthermore, combining Roman with other upcoming deep imaging observatories (such as Rubin and Euclid) will provide multiwavelength coverage that will help constrain the stellar populations (age and metallicity) of LSB sources.
High Latitude Wide Area Survey galaxies, large scale structure of the universe Galaxy stellar halos, Galaxy evolution, Galaxy formation, Extragalactic Legacy And Deep Fields, Dwarf galaxies
Morgan Fraser University College Dublin, Ireland Emma Beasor (Steward Observatory, Arizona) Finding the progenitor of every nearby transient Thanks to all sky surveys such as PanSTARRS, ATLAS and ZTF (and soon LSST), we find thousands of supernovae and other extragalactic transients each year. Of these, a few dozen will be within a distance of 30 Mpc. In these cases, searches for progenitors in archival Hubble Space Telescope images are possible - and a handful of these data have revealed the luminosity, temperature and mass of the star that exploded. This work provides a crucial observational test of theoretical stellar models, and late stages of massive stellar evolution. Moreover, it has also revealed the progenitor systems of common envelope ejection events and stellar mergers (luminous red novae), as well as the precursors of a range of non-terminal massive star outbursts (including the extragalactic analogs of Eta Car). However, major questions remain unanswered, including the existence of failed supernovae, the effect of dust on supernova progenitor mass estimates, and the variability of supernova progenitors in the decade before they explode.

One of the major obstacles to this work has been the limited availability of pre-supernova imaging of nearby galaxies. Only around a quarter of massive galaxies within 30 Mpc have some archival HST observations. Even fewer have been observed at near infrared wavelengths - which is especially unfortunate as massive red supergiants emit most of their flux at IR wavelengths. NIR observations are also less affected by reddening, making them a better indicator of stellar luminosity. Roman offers a unique opportunity to build up an archive of deep, high-resolution, multi-band imaging of nearby galaxies. This will ensure we have constraining progenitor information for every nearby extragalactic transient - for example WFI can detect a 12 solar mass red supergiant in the F129 and F213 filters at 30 Mpc in only 55 seconds! We propose a complete survey of all bright (B<-21 mag), nearby (<30 Mpc) galaxies, to obtain a full set of imaging in all WFI filters (~600 hours). Secondly, a subset of these galaxies will be monitored over 5 years, to build up a unique time series for massive star activity and pre-supernova outbursts. Ground based observations have neither the sensitivity nor spatial resolution to do this, while Romans' wide field of view is unmatched by either HST or JWST.
High Latitude Wide Area Survey stellar physics and stellar types Supernovae, massive stars, transients
Nao Suzuki Lawrence Berkeley National Laboratory NIR Nearby Supernova Survey with the Roman High Latitude Wide Field Survey We propose cadenced and coordinated observation from the ground over the Roman High Latitude Wide Area Survey. With Zwicky Transient Facility (ZTF) and La Silla Schmidt Southern Survey (LS4), we can aim to schedule one-day cadenced search of transients before and after the Roman observation on the same footprints. We will have a densely sampled light curve which characterises the supernova and 4 NIR data points for all of the supernovae over 1700 square degrees. It has been difficult for the supernova community to have IR observation even for the nearby supernovae. The flux peaks in blue (B-band) and in NIR they are a few magnitude fainter. In addition to that, to find a nearby supernova, a wide area survey is needed. With Roman depth, we can investigate supernova spectral energy distribution (SED) from optical through NIR for z<0.15 supernovae as well as AGN and variable stars.

Rest frame Opt-NIR data enables us to investigate what's powering the supernovae as well as dust properties around supernovae. Our proposed survey is complementary to the planned Roman Time domain survey and LSST. While the Roman time domain survey aims to observe redshifted SEDs in deep fields, namely rest frame optical SED, we aim to have rest frame Opt-NIR SED for the first time. LSST does not have a dense cadence and z<0.15 supernovae are too bright for LSST. Yet, the rest frame NIR supernova data points are very valuable, and as of today, no other opportunity arises in the next decade or so. We would like to maximize this opportunity and study all types of supernovae with NIR data. For Type Ia supernovae, it is known that NIR data has tighter dispersion and helps map out the large-scale structure of the nearby universe, and we will be beginning to see inhomogeneous expansion of the universe.
High Latitude Wide Area Survey stellar physics and stellar types, stellar populations and the interstellar medium, galaxies, the intergalactic medium and the circumgalactic medium, supermassive black holes and active galaxies, large scale structure of the universe Supernovae, Large-scale structure of the universe, Variable stars
Nico Cappelluti University of Miami Meg Urry, Dave Sanders Exploring the high redshift obscured accretion with Roman Our proposed study aims to shed light on the growth of the youngest, biggest, and most obscured black holes that have developed at the centers of galaxies over billions of years. These black holes are often hidden from view by thick columns of gas and dust along the line of sight, making it difficult to detect them. However, they are believed to release enormous amounts of energy during their growth, which drives the evolution of galaxies, including the Milky Way. Our multi-wavelength photometric and spectroscopic optical + IR + X-ray survey at the 50 deg2 scale, complemented with 4 filters NIR Roman-WFIRST photometry, will enable us to push the census of black hole growth to moderate luminosity, high redshift, and high obscuration. This will allow us to detect a large number of early obscured AGN and move below the "tip of the iceberg" of SMBH growth unveiled by SDSS Type-I Quasars, opening a new window for the study of black holes.

We will use three complementary approaches to assess the co-evolution of black holes and galaxies: decomposition of quasar spectral energy distributions, measuring quasar host galaxy properties using machine learning techniques, and abundance matching analysis of quasar large-scale environments. Our study will not only advance our understanding of black hole growth and galaxy evolution but will also benefit other hot topics of Roman, such as X-ray preselecting hundreds of galaxy clusters and groups, which will allow us to obtain a large sample of regions for weak lensing studies and perform very deep studies of the faintest lensed background galaxies in the early Universe. Our survey will make use of a large amount of existing and planned data sets, constituting the largest "layer" of the "wedding cake" probes of the full AGN and galaxy population. We believe that our proposed study will significantly advance our understanding of black hole growth and galaxy evolution, and we look forward to the exciting discoveries that it will bring.
High Latitude Wide Area Survey galaxies, supermassive black holes and active galaxies Galaxy evolution, Supermassive Black Holes And Active Galaxies: AGN host galaxies, Supermassive Black Holes And Active Galaxies: Supermassive black holes
Richard Collins The Internet Foundation Letting the World Watch, Comment, Contribute and Collaborate My first thought was to included a little webcam that is always on, and always pointing at the main focus of the telescope. And another one or two or three, pointing out in the general direction, or pointed by lottery. A good all sky camera in space ought to be clear enough for anyone on earth who never sees the sky, with enough optical zoom to see what most people cannot afford - a little better view than human eyes. Store at 8K or 16K, transmit to earth, add an app for zooming for people with low bandwidth. A $1000 camera (earth prices) for $ 8B people is worth roughly $8T if they all have a seat. Ten cameras always looking in different directions, but all see the whole sky at higher resolution than most people have access to standing in a cold field with a cheap telescope and no one to help. No matter what is being looked at with telescope, the webcams faithfully record and transmit that so the whole world can see. --- But little things get conveniently overlooked, all the professional astronomers and insiders soon forget they are not the center of the universe. And even the tiny real time glimpse gets shoved aside. So "many live cameras showing the whole sky" always where the "big" telescope is looking, more because they are cheap and 8 Billion-fold multiplied, while a few at a time hog the eyepiece again. That rich kid always hogged it and only pretended to share. "I'm smarter and more deserving than you, because my Daddy is rich, and has influential friends."

So adding a special feed for "everyone" is flawed from the beginning. Because it separates the people who are "working in the industry" from everyone else. Internet sciences is not recognized as a science yet, but there are more new things in "internet collaboration" than anything else. I try to write the polices and guidelines. I look at the manipulation of James Webb and Hubble still. I simply do not trust that yet another set of insiders will not conveniently forget the rest of the 8 billion people in the world. Putting all the incoming data where anyone can see is part of it. But making sure that whatever is gathered is in truly accessible form takes work. It is not where the telescope is looking, but that whatever is seen is accessible to all. NOT just "everyone don't forget to make it accessible to all in real time", but effort enough to make that real. When I was little they still had separate toilets and water fountains for black people. I guess it is separate webcams now? We get to hog the eyepiece, but have token access for those "other" people. I am writing deliberately harsh, because you so quickly conveniently forget.
High Latitude Wide Area Survey solar system astronomy, exoplanets and exoplanet formation, stellar physics and stellar types, stellar populations and the interstellar medium, galaxies, the intergalactic medium and the circumgalactic medium, supermassive black holes and active galaxies, large scale structure of the universe Global access, fairness, learning, global collaboration, the human species
Robert Blum Rubin Observatory/NSF's NOIRLab Federica Bianco (Rubin Observatory/U Delaware), Leanne Guy (Rubin Observatory), Zeljko Ivezic (U Washington/Rubin Observatory, Steve Ritz (UC Santa Cruz/Rubin Observatory), Tony Tyson (UC Davis/Rubin Observatory) Rubin proposal for a single-band Roman survey covering the LSST Wide-Fast-Deep footprint In early 2025, the Vera C. Rubin Observatory will begin executing the Legacy Survey of Space and Time (LSST, Ivezić et al., 2019 ApJ, 873, 111). The bulk of the 10-year LSST program will be dedicated to the Wide-Fast-Deep (WFD) survey, which will cover the sky to unprecedented depths in the u,g,r,i,z,y photometric bands over an area from the south celestial pole up to a declination of ~ +15 degrees. Roman and Rubin are highly complementary in wavelength, angular resolution, and time domain coverage. This proposal presents the case for a single-band Roman community survey with LSST-matched depth over the LSST WFD footprint to enhance the key science programs of both missions. The almost one order of magnitude enhanced angular resolution of Roman will boost deblending of faint galaxies and crowded regions in the Galactic plane leading to valuable and enhanced scientific impact over many of Rubin's and Roman's science goals; and would also lead to improved Differential Chromatic Refraction (DCR) modeling. Roman's extended wavelength range provides several key enhancements: improved estimates of photo-z for galaxies at all redshifts and hence improved cosmological parameter estimation; extended redshift limit for a given photo-z accuracy, thus extending the range of cosmic time for studying galaxy evolution; and improved simultaneous estimates of stellar distances and the dust column along the line of sight in the Galactic plane. Time domain data from LSST compliments Roman; flickering and variable compact objects within galaxies may be studied in new ways.

Assuming 100 sec Roman exposures with 65% efficiency (due to slew and settle), we estimate that about four months, not necessarily contiguous, are required to cover the LSST WFD footprint to mAB = 25.5 in a single band (about 1.5 mag deeper than Euclid survey). The optimal single Roman band will require quantitative optimization over several of the leading science cases outlined above.
High Latitude Wide Area Survey solar system astronomy, exoplanets and exoplanet formation, stellar physics and stellar types, stellar populations and the interstellar medium, galaxies, the intergalactic medium and the circumgalactic medium, supermassive black holes and active galaxies, large scale structure of the universe Cosmological parameters, Dark matter distribution, Near-Earth objects, Galaxy evolution, Supernovae
Seppo Laine Caltech/IPAC David Martinez-Delgado (Instituto de Astrofísica de Andalucía, Granada, Spain) Substructure Around Galaxies Within 50 Mpc Minor mergers and dwarf galaxy accretion events are far more common than major mergers in the evolutionary history of major disk (and elliptical) galaxies, and are a major ingredient contributing to the build-up of their halos, bulges, bar, spiral and even globular cluster systems. These events leave relics in the circumgalactic environment in the form of discrete tidal stellar streams and intracluster light. The investigation of such streams around galaxies, other than those in the Local Group, has just begun, and the stellar populations and types of merging (and consequently disrupted) satellite galaxies are still largely unknown.

The Nancy Grace Roman Space Telescope can probe the circumgalactic environments with sufficient depth and spatial resolution around galaxies up to at least 50 Mpc from us around the peak wavelengths of the stellar SED (near-infrared). With its large field of view Roman can perform these observations very efficiently. Combined with ground- and space-based surveys from UV to mid-IR wavelengths, the ages, metallicities and masses (and therefore morphological types) of the stellar populations of disrupted companions can be studied in a large sample of galaxies, providing much tighter constraints on the minor merging history in the CDM models of galaxy formation. A Roman Core Community survey similar to that of the High Latitude Wide Area survey would provide most likely the best opportunity to image large areas down to very low surface brightnesses in the near-infrared, thereby allowing the detection of integrated light from sufficiently well spatially resolved, individual faint stellar streams. We expect an abundance of supporting multiwavelength data (most critically, from UV to mid-IR) of large areas of the community core survey regions to become publicly available, concurrently with Roman data.
High Latitude Wide Area Survey galaxies Galaxy environments, Galaxy evolution, Galaxy mergers, Galaxy structure, Stellar populations
Simon Birrer Stony Brook University Strong lensing tomography The lensing efficiency is a function of ratios of angular diameter distances. Probing the sizes of strong gravitational lensing Einstein rings as a function of lens and source redshift allows one to probe the relative expansion history of the universe. Roman will be able to measure precisely the Einstein radius of 10'000s of gravitational lenses and a statistical tomographic study can be done with such a population of lenses and provide high-precision geometric measurements of the universe, as well as the evolving density distributions of the deflector galaxies. High Latitude Wide Area Survey galaxies, large scale structure of the universe Galaxy evolution, Cosmology, dark energy
Simon Birrer Stony Brook University Tansu Daylan Small scale dark matter structure with gravitational lenses Strong gravitational lensing is sensitive to small potentially dark perturbations in the deflector and along the line of sight. The method of 'gravitational imaging' using high-resolution imaging has been successfully used to detect perturbers otherwise not visible. Roman will have about the same resolution and depth as the Hubble Space Telescope. With the thousands of lenses from Roman, the differential substructure and line-of-sight population of dark perturbers can be statistically studies. We expect a differential signal with more signal when the line of sight is longer, for example. Such differential effects can calibrate and distinguish different signal or systematics components, such as inaccuracies in the small scale structure prediction of sub halo disruption. High Latitude Wide Area Survey galaxies, large scale structure of the universe dark matter, galaxies, cosmology
Simon Driver University of Western Australia Aaron Robotham (UWA), Sabine Bellstedt (UWA), Jochen Liske (UH), Luke Davies (UWA) The baryon contents of dark matter haloes from galaxies to groups to clusters This submission is focused on maximizing the science synergies between Roman, Ruben, the SKA and the Australian-led WAVES spectroscopic survey (2024-2029).

WAVES is the largest of the ESO 4MOST extra-galactic surveys and will obtain dense redshift measurements for over 2 million galaxies at >95% completeness to provide a unique catalogue of ~25,000 dark matter haloes on 10^11.5 to 10^15 solar mass scales. The WAVES footprint covers 1150 square degrees of sky locally (z<0.2), with deeper fields (z<0.8) covering 80 square degrees (including the 4 Ruben DDFs) with extensive radio follow-up underway (continuum and HI with MWA, ASKAP, MeerKAT and the SKA).

Alignment of the Roman medium and deep survey footprints with WAVES will provide advance knowledge of the dark matter content within these regions, opening the door for unique group-centric science.

We have 4 primary science goals but many more are enabled:

(1) a study of the baryon content as a function of dark matter halo mass using stellar masses derived from Roman/Ruben, hot gas from eROSITA (stacked), and neutral gas from ASKAP/SKA (stacked).

(2) the construction of precision spectral energy distributions for over 2 million galaxies in which eROSITA/Ruben/Roman/Herschel/SKA can be combined to provide continuous X-ray to radio coverage allowing us to disentangle AGN and star-formation flux.

(3) capitalize on Roman's depth to the study the intra-halo light (IHL; mass, distributions and spectral signature) for 25,000 groups and clusters and explore how the IHL varies as a function of halo mass and redshift.

(4) capitalize on Roman's resolution to reconstruct the distinct cosmic star-formation histories of bulges and discs for millions of galaxies with robust spectroscopic redshifts and environmental markers (using ProFuse).

A key design focus will be delivery of a multi-facility full integrated database including eROSITA/Ruben/Roman/Herschel/SKA within the WAVES regions as an Australian contribution to the Roman community.
High Latitude Wide Area Survey galaxies, large scale structure of the universe Dark matter distribution; Extragalactic Legacy And Deep Fields; Galaxy groups; Galaxy environments; Spectral energy distribution
Simona Mei APC/IN2P3/France The first epochs of cluster assembly Roman will reveal with unprecedented depth the galaxy population of clusters and proto-clusters at z>1.5, in the first epochs of cluster assembly. At present, several groups find enhanced star formation in galaxies in their cores, other groups find quenched galaxy population. Recent results show that up to z~2 the morphology density relation and passive density relation are already in place, and the fraction of mergers is higher in clusters with respect to the field (Mei et al. 2023). Roman will permit us to study galaxies in these primordial clusters in detail, in terms of morphology, stellar populations, merger activity. Surveys that can make a breakthrough in these field should cover areas (1) with deep optical observations, such as the Rubin/LSST deep fields; (2) deep Spitzer observations (Euclid deep fields, the SPTpol region covered by the SSDF survey; (3) in which clusters and proto-clusters have been already discovered. These would include clusters and protoclusters around Radio Loud AGN (QSO and high radio sources), suche as the CARLA survey, the SpiderWeb, etc., and clusters and proto-clusters discovered as line-emitter overdensities, with OII, OIII, Lyalpha emitters. High Latitude Wide Area Survey galaxies, large scale structure of the universe Galaxy evolution, Quenched galaxies, Galaxy clusters, Galaxy groups, Scaling relations
Tadayuki Kodama Tohoku University Subaru HSC-SSP team Galaxy clusters, large scale structures and galaxy evolution back to z=3~4 Growth of large scale structures (LSS) including galaxy clusters and the formation and evolution of galaxies therein, and the interplay of the two are one of the key subjects in modern extragalactic astronomy. Subaru Telescope and its unique suit of wide field instruments (eg. Hyper Suprime-Cam; HSC) have been playing key roles in mapping the LSS in the early Universe and the characterization of global/statistical galaxy formation and evolution as a function of time and environment. The wide-field survey of HSC is conducted in optical wavelength, and is thus limiting the redshift range that we can probe with rest-frame optical light to z<1.2. To extend the survey to higher redshifts (z>1.2), combining the HSC data with the wide-field NIR data such as those taken with VISTA and UKIRT is currently under-going, although the depth and the passbands are still limited.

Here we propose to largely expand the survey of LSS including galaxy proto-clusters to higher redshifts (z>2), to small masse systems (groups and filaments) and to small mass galaxies therein, with the deep and wide Roman High Latitude Wide Area Survey. The extremely large survey area of 1700 deg^2 in 4 NIR bands (F106, F129, F158, F184) and a significant fraction of it in F213, will enable us to trace the LSSs and will provide the 1000s of galaxy clusters/groups per each redshift interval (delta_z=1) out to z~4, by capturing the 4000A/Balmer break feature. The planned slitless (grism) spectroscopy is also essential to trace star forming emission line galaxies, such as H-alpha, [OIII] and [OII] emitters out to z~3 along the structures. We will be thus able to quantify the history of galaxy formation, evolution, and eventually quenching as a function of time and environment in much greater detail.
High Latitude Wide Area Survey galaxies, large scale structure of the universe Galaxy evolution, Galaxy environments, High-redshift galaxies, Galaxy clusters, Large-scale structure of the universe
Tansu Daylan Princeton University Simon Birrer Enabling investigations of dark matter substructure with Roman Static strong lenses are rare objects with high cosmological information content on the matter content of galaxies and the expansion of the Universe. In particular, galaxy-galaxy lenses allow us to detect substructure in the main lens and test LCDM at small scales. Compared to those observed by the Hubble Space Telescope, The Roman Space Telescope can significantly extend the sample size of galaxy-galaxy strong lenses with comparable or better image quality. This extension will enable precise measurements of the dark matter substructure and investigations of the microphysics of dark matter as a function of redshift.

The desirable observational features for this investigation are high (<0.1 arcseconds) angular resolution and large sample size. Roman WFI offers a wide range of filters, from optical to infrared. In particular, F062 and F087 filters yield 0.058 and 0.073 arcseconds, respectively. Therefore, we recommend that during the execution of the HLWAS, the telescope takes additional deep (i.e., 2-3 times the typical survey depth) imaging data on known galaxy-galaxy strong lenses using the F062 and F087 filters.
High Latitude Wide Area Survey galaxies, large scale structure of the universe dark matter distribution, Galaxy dark matter halos
Ting Li University of Toronto Exploring Milky Way's stellar streams, dwarf galaxies and star clusters with Roman Roman will be powerful tool to explore the substructure and satellite systems in the Milky Way. With its high precision photometry to high depth, well-calibrated astrometric measurements on proper motion, we will be able to use them to study the formation history of the Milky Way as well as shed light on the nature of dark matter. It will be very useful if the footprint and survey strategy for the Roman high-latitute survey would be carefully designed to coordinate with the planned or existing surveys such as the LSST on Rubin Observatory, and DESI survey at KPNO, etc., to maximize its scientific potential. High Latitude Wide Area Survey stellar populations and the interstellar medium, galaxies Galaxy dark matter halos, Dwarf galaxies, Galaxy halos, Globular star clusters, Star clusters
Tsuyoshi Terai Subaru Telescope, National Astronomical Observatory of Japan Fumi Yoshida Water Ice Abundance on Trans-Neptunian Objects Trans-Neptunian objects (TNOs), a small body population beyond Neptune's orbit, are located far from the sun where it is cold enough to retail volatile materials on their surfaces. The composition of the surface ices provides essential information about the thermal/chemical histories of primordial planetesimals in the outer solar system regions, and allows us to promote better understanding of the physical and chemical conditions in the protoplanetary disk in the early solar system. Water ice is known to be contained on large-sized TNOs (except for several of the largest objects such as Pluto, Eris, Makemake, and Sedna covered by methane ice) as the most common icy components, while none or only small amounts of water ice were detected on most of the other TNOs excluding the Haumea collisional family members. It is still uncertain whether such objects truly lack water ice on their surfaces, or it is just obscured by some impurities such as dark particulates. We are planning to use the survey data with WFI for investigating water ice abundance on known TNOs of various sizes. Since water ice has a characteristic absorption band at 1.5 um, it is possible to diagnose the presence of water ice on their surfaces by using the photometric data with the F106, F129, and F158 filters. High sensitivity of Roman/WFI allows us to perform this observation for small-sized TNOs down to 100 km in diameter. In addition, slitless prism spectroscopy can measure the absorption depth more precisely. We would like to observe more than 100 TNOs to statistically study the relationship between the water ice abundance and the body size, dynamical class, optical colors, and other properties for TNOs. High Latitude Wide Area Survey solar system astronomy small solar system bodies, trans-Neptunian objects, water ice
Tsuyoshi Terai Subaru Telescope, National Astronomical Observatory of Japan Fumi Yoshida Size Distribution of Small Trans-Neptunian Objects Trans-Neptunian objects (TNOs), a small body population beyond Neptune's orbit, are remnants of the accretional phase of the planet formation processes in the early solar system and have been continuously modified by mutual collisions. Their size distribution for large body sizes is primarily characterized by the accretion process and thus its shape (i.e., power-law slopes) can be different among the dynamical populations which have different origins. In contrast, below about 100 km in diameter, the size distribution slope is expected to be universally altered through the collisional evolution. The transition size is not determined yet. WFI's wide field-of-view and high sensitivity are suitable for detecting a large number of faint TNOs. We will precisely examine the luminosity function of TNOs down to 50 km in diameter as faint as about 26.0 mag in the F062 band using the huge data set for High Latitude Wide Area Survey and to determine the size of a break in the power-law slope corresponding to the transition from a primordial to a collisional equilibrium population. High Latitude Wide Area Survey solar system astronomy small solar system bodies, trans-Neptunian objects, size distribution
Wei Leong Tee University of Arizona Xiaohui Fan, Feige Wang Revealing the Elusive: Hunting for Low-luminosity, Low-mass, High-Redshift AGNs Low-luminosity, low-mass, high-redshift quasars and active galactic nuclei (AGN) are crucial for understanding the origin and early growth of supermassive black holes (SMBHs). This population may represent the intermediate stage of rapid black hole growth. Studying their accretion properties and black hole - galaxy co-evolution will also provide a comprehensive view on multiple scale interactions involving AGN, from central SMBHs to the intergalactic medium (IGM). However, the current generation of wide-field optical and near-IR surveys have limited our ability to discover quasars at low luminosity due to sensitivities in both optical dropout bands and near-IR continuum bands. The lack of observational evidence for these sources can bias our understanding of the different SMBH growth models.

The identification of high-redshift AGN relies on a distinct Lyman break, which shifts from the optical to near-IR wavelengths at z > 6.5. The RomanHigh-Latitude Wide Area Survey and High-Latitude Time Domain Survey, using its near-IR Wide Field Instrument (WFI), is expected to detect faint AGN in the early Universe. A combined deep optical-Roman survey will provide unprecedented depth and sensitivity, reaching ~ 26-27 ABmag across the entire wavelength of interests and over large sky area. This powerful multi-band tool will enable the search for AGNs at z=7-10 across a broad range of luminosities. Variability has proven to be a powerful tool for identifying low-luminosity AGNs in high-redshift Universe. Multiple passes over survey duration will provide sufficient time domain information to determine AGN variability. Additionally, time-domain surveys will measure the proper motion of faint dwarfs, which are a primary contaminant population for AGN selection. We expect Roman to eventually discover the earliest quasars and AGNs, up to redshift 10, and yield the largest sample of hundreds of quasars at z>7 for detailed multi-wavelength followup studies of early SBMH growth and intergalactic medium evolution.
High Latitude Wide Area Survey supermassive black holes and active galaxies Supermassive black holes, Low-luminosity active galactic nuclei, quasars, Brown dwarf stars
Yuichi Harikane University of Tokyo Masami Ouchi Studying the Cosmic Dawn at z>10 with Roman Understanding the galaxy formation in the early universe is one of the frontiers of modern astronomy. Recent JWST observations have found many galaxies at z>10 whose number density is surprisingly higher than theoretical model predictions, suggesting a possibility that the physics in the early galaxy/star formation is fundamentally different from that in lower redshift universe (e.g., see discussions in Harikane+23, ApJS, 265 5). However, due to the small field-of-view of JWST/NIRCam, the number of such high redshift galaxies is limited, which prevents us to conduct statistical studies.

Here, we propose to include the F158, F184, and F213 imaging observations in the Roman High Latitude Wide Area Survey. By achieving the depth of 26.4 ABmag (F213-band, 5sigma, point source), the High Latitude Time Domain Survey will provide samples of 200k and 700-10k galaxies with MUV<~-22 mag at z=12-14 (F158-dropout) and z=14-16 (F184-dropout), respectively, allowing us to investigate the bright-end of the UV luminosity functions and massive galaxy formation in the early universe at z>10 with unprecedentedly large survey volumes that JWST/NIRCam cannot reach. Thanks to their brightness, we can not only conduct statistical studies (e.g., UV luminosity function, cosmic SFR density), but also investigate detailed properties (e.g., chemical properties, dynamics, stellar populations) by spectroscopically following up these galaxies using JWST/NIRSpec, MIRI, and ALMA. By including these observations, we can efficiently add valuable science cases for early galaxy formation in this core-community survey.
High Latitude Wide Area Survey galaxies Galaxy formation, Galaxy evolution, High-redshift galaxy
Yuichi Harikane University of Tokyo M. Oguri (Subaru Advisory Committee, Chair), T. Kodama, M. Ouchi, A. Nishizawa, H. Miyatake, Tsutomu T. Takeuchi, K Nakajima, Tomomi Sunayama、Masayuki Tanaka, A. K. Inoue Maximizing the Synergy between Roman and Subaru The combination of joint Roman and Subaru observations has the potential to enable transformative science that cannot be done by either telescope alone. The wide field of views of Subaru/Hyper Suprime-Cam (HSC, 1.5 deg2) and Prime Focus Spectrograph (PFS, 1.2 deg2) have excellent synergies with Roman's wide field instruments. Roman will image the 0.6-2.1um sky with unprecedented depth and area, and Subaru/HSC will provide broad-band and unique narrow- and medium-band images at 0.4-1.0 um complementary to Roman. The Subaru/PFS will conduct massive spectroscopic observations (~2400 fibers/pointing) with the medium resolution (R~3000) at 0.38-1.26um, which will complement Roman's grism spectroscopy at 1.0-1.9um with R~300. The director of the Subaru Telescope and Subaru Advisory Committee already agreed with NASA to commit 100 Subaru nights to the Roman-Subaru synergetic observations.

To enable the Roman and Subaru synergetic observations, we propose to observe northern and equatorial fields that can be observed with Subaru. The possible field candidates include Chandra Deep Field South, North Ecliptic Pole, and COSMOS, all of which are accessible from Subaru and with low Galactic extinction. By taking advantage of the unique capabilities of Subaru/HSC and PFS, the Roman and Subaru/HSC+PFS synergetic observations will allow us to investigate various important science cases to understand galaxy formation and evolution, such as discoveries of luminous early galaxies at z>10 (with deep non-detection bands from Subaru to eliminate interlopers) currently showing a tension with theoretical predictions, large scale structures and protoclusters at z=2-15, mapping the progression of cosmic reionization with improved redshift precision of galaxies enabled with HSC/narrow-bands+Roman, the most massive galaxies to study their possible tension with the LCDM cosmology up to z~4, and metal-poor star-forming galaxies in the early evolutionary phase at z=1-2 possibly hosting primordial structures such as Pop-III stars, all of which can be only identified in the wide-area Roman and Subaru synergetic observations. Furthermore, the medium-band images from Subaru/HSC will greatly improve the accuracy of the photometric redshift which is crucial for weak lensing cosmology. Thus, choosing fields that can be accessible from Subaru as the core community survey field will maximize the scientific outputs from Roman and Subaru synergetic observations.
High Latitude Wide Area Survey galaxies, the intergalactic medium and the circumgalactic medium, supermassive black holes and active galaxies, large scale structure of the universe Galaxy evolution, Galaxy formation, Cosmology, Large-scale structure of the universe, Reionization
Евгений Русский, Москва Федор Васильевич Шугаев Применения метода Математический Микроскоп в астрономических исследованиях In fact, the MM method implements a new or third method for solving systems of linear equations y=Ax with the main unknown AF A. Fundamental Physical Principle (FPP) of solving the main MM problem. MM worked well on astronomical images, for which the presence of point objects in x-image solutions is natural. High Latitude Wide Area Survey exoplanets and exoplanet formation, stellar physics and stellar types, stellar populations and the interstellar medium, galaxies, the intergalactic medium and the circumgalactic medium, supermassive black holes and active galaxies n/a