GALEX Guest Investigator Cycle 1 Abstracts
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“Our goal is to image with GALEX two galaxy clusters at z=0.2, as well as the large scale structure in which they are embedded. This is the lowest redshift at which evolution of the cluster galaxy population becomes noticable, yet it is the highest redshift at which HI in emission can be detected. We are imaging both clusters in HI with the WSRT, down to a HI mass comparable to that of the LMC, surveying a volume of 70,000 cubic Mpc, comprising a wide range of environments. Abell 963 is a lensing Butcher-Oemler cluster with a large blue fraction while Abell 2192 is less massive with more substructure. GALEX measurements will provide starformation rates of all HI-detected galaxies forming stars close to the Kennicutt relation, and even detect galaxies that form stars at a factor 6 lower rate, providing useful upper limits on enhanced or diminished star formation activity during the last few 100 Myrs. These are the very timescales on which dynamical and gas-gas interactions work. By combining these GALEX observations with optical and radio continuum images, optical spectroscopy and HI imaging, CO spectroscopy and SPITZER IRAC and MIPS observations it will be possible to elucidate the physical mechanisms that cause the environmentally-driven evolution of galaxies."
“To investigate whether star formation occurs in situ in intergalactic gas clouds, we propose to use GALEX to conduct a deep search for star formation in several intergalactic H I gas clouds that are not obviously tidal debris or extended disks. Using a combination of high-resolution ultraviolet spectroscopy from HST and deep VLA 21cm emission mapping, we discovered several of these clouds in a recent study of the field of the low-z QSO PG1216+069, a sight line that passes through the outskirts of the Virgo cluster near the X-ray bright NGC4261 group. Our HST+VLA observations provide unique constraints on these clouds such as detailed kinematics and metallicity information. By observing these clouds with GALEX, we will probe the fundamental nature and implications of intergalactic H I clouds. If UV emission is detected or not will place constraints on the source of metal enrichment in the clouds, an important aspect of galactic feedback processes. If emission is detected, we will investigate whether the clouds are beginning to form stars and transform into galaxies or if the star formation is fading. We will complement the PG1216+069 data with observations of another large Virgo H I cloud, H I 1225+01."
“Long-period comets are some of the least
evolved bodies in the solar system. Their study is therefore central to NASA's
Solar System strategic science goal 3C:""Advance scientific knowledge
of the origin and history of the solar system...."" On UT 2005 March
1, GALEX observed comet the long-period comet C/2004 Q2 (Machholz). Preliminary
reduction of the data shows that several scientifically important atomic lines
and molecular bands are easily detected, including C I 1561 A
and 1657 A, CS 2576 A, and OH 3080 A. Emission from S I, CO, and
“GALEX observations provide a view of star formation in galaxies that is an important compliment to the H-alpha and mid-infrared measures. For a sample of star-forming dwarf galaxies in the Bootes field, the calculated UV star-formation rates (SFRs) are significantly larger than the H-alpha and mid-infrared rates even though the UV has not been corrected for extinction. The large UV SFRs pose a mystery that we hope to address by observing a more statistically significant sample. Is this UV SFR excess a problem with the SFR conversion in low metallicity galaxies or is it an indication that some of the gas and dust has been removed from the star-formation regions in these systems? These observations will have 2 primary goals: (1) determining the properties of the interstellar medium surrounding star-formation regions by combining UV as a probe of the young stars, H-alpha as a probe of the hot gas, and infrared as a probe of the warm dust, and (2) measuring the effect of metallicity on the standard calculation of SFR."
“Hydrodynamical simulations of the formation and growth of large scale structure predict the existence of a cosmic web of warm-hot intergalactic gas in the low-redshift universe. We will use GALEX to image the fields around four well-studied QSO sight lines exhibiting low redshift ionized oxygen (O VI) lines, which are excellent tracers of hot gas with log[T(K)] = 5-6. The sight lines are long enough (z ~ 0.1-0.3) to intercept intergalactic absorption features, yet the absorbers and galaxies are near enough to study galaxy-absorber relationships and the individual components of galactic systems. In conjunction with our ground-based galaxy redshift inventories, our Cycle 2 GALEX data for 5 sight lines, and archival GALEX data for one sight line, we will:  Derive the UV colors and star-formation properties of the galaxies at the redshifts of the absorption line systems.  Correlate these quantities with the absorber properties (hot gas content, metal content, line widths) and sight line impact parameters.  Compare the star-formation results with galaxy morphology as derived from both ground-based images and archival HST/WFPC2 data.  Identify faint blue galaxies, low surface brightness regions with young stars (e.g., tidal tails), and galactic halos/winds of large galaxies for follow-up spectroscopy with large ground-based telescopes and high resolution imaging with HST/ACS. We will test whether the absorbers arise in hot gas produced in galactic environments (e.g., starburst outflows, galactic coronae, tidally stripped streams, intragroup medium) or are part of a more generally distributed warm-hot IGM heated by the gravitational collapse of the cosmic web. This study extends our Cycle 2 program aimed at defining the distribution of metals outside galaxies, the evolution of galaxies in proximity to intergalactic gas, and the effects of galactic feedback processes on the morphology of the cosmic web."
“We propose to image 8 bright Barium (Ba) dwarfs in the FUV and NUV in an effort to detect their putative white-dwarf (WD) companions. The prevailing theory for the formation of both Ba dwarfs and giants suggests that they acquired their enhanced s-process abundances via mass transfer from an Asymptotic Giant Branch companion, which is now a white dwarf. There is good evidence to suggest that Ba giants evolve from Ba dwarfs; however, to date WD companions have been detected for Ba giants, but not for Ba dwarfs. Our current ideas regarding the origin and evolution of both Ba giants and dwarfs may therefore stand or fall according to the outcome of this observational program."
“The outer edges of galaxies present an extreme environment for star formation. Dwarf irregular (dIm) galaxies already challenge models of star formation because of their low gas densities, and the outer parts present a particularly difficult test. We have obtained ultra-deep V-band images of 5 dIm in order to examine the star formation and stellar populations in extreme outer disks. We propose to obtain deep UV images to trace and characterize star formation at disk edges where Halpha is no longer detectable. We will determine the star formation rate with radius and its relationship to the gas and stellar surface densities, examine the star formation histories through multi-wavelength colors, and compare characteristics of star forming units at the edges to those in the inner galaxy."
“Dwarf galaxies seem so simple. Yet the processes that lead to star formation on galactic scales are poorly understood. We have, therefore, embarked on a comprehensive study of a sample of dwarf galaxies spanning a range in luminosity in order to unravel the processes which govern star formation in these tiny systems. GALEX UV imaging plays a pivotal role as UV images will reveal star formation in the outer disks where Halpha is a poor tracer of star formation. The GALEX data, combined with our optical/IR/radio data, will enable us to answer the following questions: 1) How is star formation occurring in the outer parts of dwarf galaxies, where the gas is gravitationally stable? 2) And, what happens to the star formation process at breaks in the stellar light profiles?"
“Among cataclysmic variables with highly magnetic white dwarfs (polars) are a group with extremely low accretion rates, with accretion likely only via magnetic capture of the stellar wind from the secondary. In Cycle 1, we successfully used GALEX NUV and FUV light curves to show that after 7 yrs of no mass transfer in the polar EF Eri, there is still a large and highly variable source of UV light that could be due to a hot spot in combination with another source such as cyclotron. We propose similar time-resolved UV imaging of 3 systems in the wind accretion regime in order to understand the nature of this UV source. The results impact the evolution and ages of accreting white dwarfs in binaries."
“Supernova (SN) explosions play a pivotal
role in triggering, driving, and (later on) inhibiting further star formation
in galaxies. In fact, the combination of new observations and refined modelling shows that the little-understood and poorly
constrained contribution of SNe to galaxy evolution processes (often hidden
under the generic name of ``feedback'') is probably the weakest link in our
understanding of structure formation in the Universe. Setting observational
limits on the rate, environments, and energy output of high-redshift SNe is
therefore one of the main science drivers of recent Hubble Space Telescope
(HST) legacy programs, as well as of future missions like the James Webb Space
Telescope (JWST). However, observations of high-redshift SNe in the optical (by
HST), or in the near-IR (by JWST), actually sample the rest-frame UV of these
objects. Thus, proper interpretation of these observations requires knowledge
about the UV properties of SNe. Such UV data are also powerful probes of the SN
environment, progenitor structure and explosion mechanism. Unfortunately, UV
spectroscopy of local SNe of all types, which can only be obtained from space,
is scarce. Previous efforts using HST and IUE were focussed on a single SN sub-type,
“We propose to obtain GALEX NUV and FUV images of SDSS J1230+020, a dwarf galaxy (M_B = -14.6) that has lost all available fuel for star formation. These images will allow us to determine whether this galaxy formed stars in a single starburst 3.5 Gyr ago or has a more complicated star formation history similar to those of the Local Group dwarf spheroidal galaxies. Understanding the star formation history of this unique probe of dwarf galaxy evolution will provide the missing link between the starbursting dwarf galaxies at z=1 and the dwarf spheroidals of today. These observations will also allow us to test the viability that this tiny galaxy's starburst wind is responsible for a Lyman-alpha + metal absorption line system in the spectrum of 3C 273, which is located 11 arcminutes away."
“The Cosmic Origins Spectrograph Science
Team for IGM studies proposes to observe the bright QSO/starburst galaxy pair,
SBS1108+560/M108 for the following purposes: 1. To measure the FUV brightness of the QSO to determine whether an HST/COS
observation is viable and to set its exposure times. 2. To determine the
locations of the brighter star forming regions in the disk of M108 to compare wth high resolution HI 21cm, H alpha and soft X-ray
continuum maps which show supershells, line-emitting
loops and extra-planar clumps of hot gas. 3. To use the relative extinctions of
near-side and far-side star forming regions to determine the orientation of
M108 in space. This determination is required in order to correctly interpret
the kinematics of any QSO absorption line system(s) found in our
“Ancient cool evolved stars show signatures of chromospheric heating and mass loss. The mechanisms responsible for both these forms of stellar activity remain a puzzle. While acoustic heating generated by convective motions is a potential heating mechanism, magnetic fields appear to be required to drive mass loss. However, the rotationally induced global magnetic dynamo, present during the main-sequence, is expected to decay through angular momentum loss in both the coronal wind, during evolution towards the red giant branch, and during mass loss during the ascent of the giant branches. We propose a search of the GALEX Archive to obtain FUV and NUV photometry of metal-poor field giants. Comparison with synthetic photometry from MARCS photospheric models will help establish the levels of chromospheric activity as a function of stellar evolution. A comparison of the FUV and NUV fluxes with theoretical predictions may reveal whether acoustic heating alone can explain the chromospheric emission."
“Many of the new and future UV telescopes are photon counting instruments that are more sensitive to fainter magnitude objects than many of their predecessors. It has been recognized for many years the necessity for faint UV standards in order to calibrate these sensitive UV telescopes. However, no such standards have been clearly established. We propose to combine SDSS spectra of DA White Dwarfs with Swift UVOT ubv photometry and Swift UVOT and GALEX UV photometry. We will then compare this spectroscopic and photometric data with models of pure hydrogen atmospheres in local thermodynamic equilibrium in order to establish faint UV standards."
“We propose a two-phase archival study of post-starburst quasars (PSQs) employing GALEX photometry. PSQs are broad-lined AGN that also possess the spectral signatures of massive, moderate-aged stellar populations (masses in excess of a billion solar masses and ages of hundreds of Myrs). This class represents several percent of the quasar population and may explicitly reveal how black hole/bulge correlations arise. Younger versions of PSQs would have a larger population of young stars, but would likely be dust enshrouded like ULIRGs. Our sample of 609 z<0.75 spectroscopically-selected PSQs stems from the SDSS DR3. A subsample of 26 PSQs (0.25 < z < 0.45) have been observed with several observatories including optical images from HST/ACS, infrared images from IRTF, infrared spectra from Spitzer/IRS, and optical spectra from KPNO and/or Keck/LRIS. In the first phase of our study, we wish to fully characterize the SEDs of PSQs using this smaller sample. This will provide a context in which to understand this new class and provide potential relationships to other objects like ULIRGs. In the second phase, we wish to use the full sample to investigate the young stellar content of PSQs. (Of the 609 PSQs, 444 are covered by existing GALEX observations largely from the AIS and MIS, and 355 are detected. In a supplementary exercise, we plan to stack the images of non-detected PSQs to measure or place limits on the UV flux.) While the optical spectroscopy from SDSS and KPNO/Keck give us an estimate on the ages and masses of the evolved stellar population as well as preliminary measurements of the AGN (e.g., black hole mass, accretion rate), they tell us nothing about the young stellar content or the star-formation history. The addition of UV data will allow us to estimate the ages and masses of younger stellar populations for a statistically interesting sample, helping us to understand the distribution of star-formation histories of PSQs."
“We propose to complete a program of targeted 1.5 ksec GALEX observations of a sample of nearby, low mass galaxies detected in the HI line by the currently ongoing Arecibo Legacy Fast ALFA (ALFALFA) survey. Significantly advanced in comparison with earlier blind HI surveys, ALFALFA is specifically designed to detect hundreds of low mass, gas rich systems throughout the Local Supercluster. As members of the ALFALFA team, we are undertaking a multiwavelength study of the lowest mass ALFALFA detections (log HI mass < 8.4 at cz = 3000 km/s and HI velocity width less than 100 km/s) to determine their cosmic abundance and distribution and their characteristics as a galaxy population. In combination with optical broad band and H-alpha imaging, NIR/FIR and radio continuum fluxes, and HI line measures (fluxes, redshifts and widths), GALEX UV observations will yield star formation rates and ages and trace the sites of the youngest stellar populations, even in systems where the current/past star formation activity has been very low. In combination with our Cycle 3 program (GI3-84) and images retrieved from the GALEX archive, our final sample will be adequate in size to allow a study of trends within the class of low HI mass dwarfs and possible variations in those trends with environment within the Local Supercluster."
“The first known pulsating white dwarf in an accreting close binary system (GW Lib) underwent an outburst in April, 2007. We aim to follow the pulsation spectrum as the white dwarf cools back to to its quiescent temperature from its heating due to the outburst which should take about 3 years. As it cools, it should re-enter the instability strip and we can witness changes in the driving mechanism and detect modes that are excited by the temperature changes. The higher pulse amplitude in UV vs optical and the available time-tag mode makes GALEX the instrument of choice. The data in 2008 will be combined with our DOT time in May, June 2007 to provide coverage of the largest cooling that takes place in the year following outburst. Since the few known systems only outburst every 20-30 yrs, this is the first opportunity to accomplish a study of this type."
“We have been engaged in a ground based U-band survey of a sample of very large scale length (> 5 kpc), relatively isolated, face-on disk galaxies that exhibit strong spiral structure, in order to identify potential candidates like the remarkable galaxy NGC 300, which has recently been shown to exhibit a continuous exponential disk over 6-10 optical scale lengths. Our U-band data shows coherent exponential disks over 4-5 scale lengths and we seek to use the excellent power of GALEX in detecting low surface brightness stellar populations to better show the true extent of these disks, The detection of such extended stellar distributions would provide strong confirmation that a) star formation does occur in very low surface density environments, b) disk galaxies have dynamical continuity that exceeds that which can currently be understood theoretically and c) such extended environments are the parent population of intergalactic stars/baryonic debris as these environments are disrupted through hierarchical clustering processes. If the NGC 300 phenomena can be shown to exist in other structures then this represents a profound theoretical challenge to both our understanding of disk galaxy formation and assembling as well as star formation. Two added bonuses of these observations are 1) the discovery of another laboratory to potentially study the dynamics of objects located in a very low gravitational acceleration environment and 2) obtaining NUV morphologies of very large disk galaxies, (which are likely the objects most easily detected at high redshift) at the same rest frame stellar population light as high redshift disks. Convolving the images to the same physical resolution would then allow for a direct comparison of galaxy morphology in large disk galaxies at z=1 compared to z=0.."
“We propose to analyze GALEX-SDSS observations to measure enhanced star-formation in the largest existing sample of close separation (< 20 kpc) mergers in the local Universe. In order to do so we define three samples: (1) 126 visibly interacting galaxy systems selected visually from the Sloan Digital Sky Survey (SDSS) Data Release 4 (DR4); (2) 122 kinematically associated galaxy systems (within 300 km/s); and (3) a similarly sized control sample of galaxies selected with the same distribution in stellar mass and environment. We will compare the star-formation rate per unit stellar mass (specific star-formation rate) in the first two samples relative to the third to quantify the enhancement due to interactions. While other investigators have explored this question in the past, our joint GALEX-SDSS sample represents the largest existing sample with very close separations (less than 20 kpc) and star-formation rate estimates. With a sample this large, we have good statistics for a range of pair separations, galaxy pair types, galaxy merger types, total masses, and mass ratios, and can evaluate the dependence of the star-formation enhancement on these various properties. Because of our relatively well-understood selection function, we will also be able to evaluate the overall contribution of mergers to the total star-formation rate density today. Of our first two samples, 24 of them have Spitzer IRAC and/or MIPS photometry available, which we plan to use to explore how the ""hidden"" star-formation components alter the conclusions one would draw from the UV alone."
“Most galaxies in the universe are members of groups. Groups are, therefore, an important laboratory for studying the processes associated with galaxy formation and evolution. To better understand the group environment and its role on galaxy evolution, we are carrying out the first detailed optical, X-ray and far-IR study of an unbiased sample of nearby groups. Each group in our sample is being observed with the IMACS wide-field multi-object spectrograph on the Magellan I telescope, XMM-Newton and Spitzer. Our existing data suggests that a large fraction of group galaxies are undergoing active star formation and that the level of star formation is linked to the evolutionary stage of the group itself. To obtain robust star formation estimates over larger regions around each group, we propose a GALEX imaging survey of our group sample. The proposed GALEX observations will probe to very low star formation rates allowing an accurate census of star formation for galaxies in the group and galaxies encounter the group environment for the first time."
“We propose to study the effect of the cluster environment on galaxy evolution by observing a collection of groups at z = 0.37 that will collapse to form a cluster with a mass comparable to that of Coma. Chandra observations provide the mass estimate of the 4 distinct groups and extensive optical spectroscopy is used to identify ~ 170 member galaxies across the field. We also have Spitzer MIPS observations to assist in measuring star formation rates and an HST ACS mosaic to measure galaxy morphologies. In this system, we have galaxies in a low density (group) environment that are the manifest progenitors of galaxies currently located in a high density (cluster) environment. The test is therefore straightforward: Do the properties (morphologies, star formation rates, star formation histories) of these group galaxies already match those seen in local clusters or are they yet to be ""transformed""?"
“We propose to obtain GALEX FUV and NUV images, with 4.5 ksec (3 orbit) exposures, at locations correponds to 20 of the 21 CCD fields of the Kepler Mission. The Kepler Mission will observe a 105 square degree area, essentially continuously for 4-6 years looking down the Orion spiral arm in the direction of Cygnus/Lyra, with the goal of measuring the properties of hundreds of transiting extrasolar planets. To achieve this goal Kepler will observe well over 100,000 stars in broadband optical light. Observations of significant numbers of non-prime-science targets (stars, AGN, or whatever types of interesting object people propose) will be possible. We will use our GALEX images to identify previously unrecognized active stars in the V = 9-15 range, that will be potential Kepler targets, by their FUV excesses compared to inactive stars. MANY other objects that could be of interest to the wider astronomical community will be present in these fields."
“We propose deep NUV/FUV imaging of the AKARI North Ecliptic Pole (NEP) Deep Field to compare the evolution of obscured and unobscured star formation and accretion power in galaxies from z=0 to 1.5. AKARI has, as a legacy project, the deepest near- and mid-IR observations ever made. Its IRC has 4 mid-IR bands filling in the Spitzer MIPS/IRAC factor-of-3 wavelength gap, which includes the distinguishing spectral features of hot dust, silicates, and PAHs. Combining the 9-point mid-IR spectra of these features with our existing ultra-deep broadband BVRIz Subaru Suprime-Cam imaging of the same field, and the proposed GALEX observation, we will form the first complete sample of 2500 galaxy FIR/MidIR/Near-IR/Optical/NUV/FUV SEDs. And we will overcome the largest bottleneck in all deep field studies of galaxies, since they will nearly all have reliable redshifts. No comparable survey can be done with any telescopes on Earth or in space for the forseeable future. The mid-IR spectra will be used to classify the quiescent or starbursting galaxies and AGN. Combining this with FUV photometry will then determine their extinctions and the intrinsic bolometric power they emit from star formation and black hole accretion. This will be the first complete census, independent of obscuration, from the current epoch back to 10 Gyrs ago. By comparing independent UV and IR estimates, we will determine how much of the total AGN and starburst populations is being missed altogether by UV/optical selection. Our sensitive near-IR photometry will provide estimates of stellar masses; while clustering, in the 15 Mpc (projected) diameter of the NEP at z ~ 1, will reveal the characteristic dark matter halo masses of these galaxy populations."
"A direct and independent verification of the GALEX image-mode photometric calibration is proposed using archive observations of an ensemble of DA white dwarfs. The proposed method involves synthetic photometry and has already been successfully employed for SDSS ugriz bands. The results of this determination will directly relate GALEX magnitudes to the most recent realization of HST photometric scale (Bohlin 2007) as well as the SDSS ugriz magnitudes. This method has the ability to conduct a first order evaluation of the wavelength dependence of the pre-flight imaging-mode band passes. The proposed effort is not intended to replace or supplant the existing GALEX calibration but to evaluate any differences between observed and predicted fluxes."
“The nearby, young (600 Myr) Hyades cluster is an important testing ground for theories of stellar activity and flares, whose associated chromospheric and coronal emissions are particularly conspicuous at high energies. The Hyades region has been imaged numerous times by soft X-ray observatories, beginning a quarter century ago with Einstein, continuing with ROSAT, and more recently Chandra and XMM-Newton. However, FUV observations -- particularly of key energy balance and flare tracer C IV 1550 -- have been hampered by faintness of the cluster members and the usual limitation to observe them one at a time. Here, we propose to continue our Cycle 3 program by imaging three rich fields in the Hyades with the GALEX grisms to capture C IV (and Mg II 2800) in 30, or more, cluster members of late spectral type (F-K), mostly main sequence stars. The controlled sample will strongly leverage our understanding of high energy processes and flare outbursts in Sun-like stars, especially in the crucial age range of our own solar system when primitive planetary atmospheres were strongly eroded by coronal ionizing radiations and mass ejections. The spatial multiplex advantage, high sensitivity, spectral isolation, and long stare capability of GALEX are ideally suited to the project."
“At high redshifts, significant effort has been focussed on bridging two samples of galaxies, the Lyman Alpha Emitters (LAEs) and the Lyman Break Galaxies(LBGs). While the two populations selected by different methods display comparable star-formation rates, metallicities, etc., the precise connection between LAEs and LBGs remains an open question. One exciting discovery from GALEX is a sample of local, intensely star-forming galaxies: Ultraviolet Luminous Galaxies (UVLGs). A subset of UVLGs, the supercompact UVLGs, show striking similarities to LBGs. The grism technology of GALEX allows us to investigate the Lyman alpha emission properties of these local LBGs, thereby providing timely insight into galaxy formation at high and low redshift."
“AM Canum Venaticorum (AM CVn) stars for a small group of ultra-compact binaries consisting of white dwarf and a degenerated or semi-degenerated donor. They are not only unique laboratories for accretion disk under extreme conditions, but also the only known source population which the gravitational wave mission LISA will be able to detect. As the gravitation wave radiation increases steeply with decreasing orbital separation, short period AM CVn are expected to dominate. Here we propose to search for the shortest period systems (P_orb<20min) in the Medium Imaging Survey archival dataset. We identified ~3000 candidates in the GALEX-SDSS color phase space. For these, we intend to extract NUV light curves in order to search for typical orbital or superhump signatures. Promising candidates will be pursued with ground-base large optical telescopes. We expect to find between 20 and 30 new systems, thus potentially trippling the currently known population."
“Most of the diffuse cosmic Halpha
radiation is believed to be produced by the warm ionized medium (WIM) that is a
main component of the interstellar medium of the Galaxy. However, it has been
claimed that there are cases where all or most of the Halpha radiation is due
to dust-scattering by of Halpha illuminating sources (Mattila et al. 2007). The dust scattering features of Halpha at high-latitude clouds
observed by Mattila et al. (2007) should have the
counterpart in the UV wavelength bands, since the diffuse UV background is
known to be produced mostly by dust scattering. We thus propose to search for
the UV counterpart of the Halpha in GALEX archival data and to investigate
whether the feature can be explained self-consistently with a dust scattering
scenario or not. The analysis of high-latitude clouds will provide strong
evidence on the significance of dust scattering in Halpha light. It will impacts our understanding of the heating and ionization
sources of WIM, and the significance of the scattered Halpha. The analysis of
high-latitude clouds will also provide the scattering properties of dust grains
on the scale of individual clouds. This is important since the scattering
properties have been investigated mostly on a large scale and the dust
scattering models have shown significant disagreements at FUV. We will analyze
the GALEX archival data toward high-latitude clouds with a
“Early-type galaxies have a hot X-ray
emitting interstellar medium, along with cooler gas that is detected from
optical emission lines or from dust emission and extinction. Whether or not the
cooler gas is a consequence of modest cooling flows, it does not accumulate, as
large amounts of mass are not present. The implication is that the cool gas is
consumed in low-level star formation, a phenomena that has received little
study due to technical difficulties that are overcome uniquely by GALEX. In an
elliptical, the best indicator of low-level star formation is the P-Cygni line of CIV 1550 A, produced in stellar winds of
“We propose to conduct a wide-field UV survey of 29 X-ray luminous galaxy clusters at z~0.2. these 29 are drawn from the 100 clusters under intense multi-wavelength study as part of the Local Cluster Substructure Survey (LoCuSS). A 29 have high quality wide-field weak lensing data from Subaru, plus deep HST imaging of the cluster cores. the primary science goal is to achieve a definitive survey of quenched star formation in passive spiral galaxies (objects in transition from spiral to S0 morphology) in local galaxy clusters. The combination of the proposed GALEX data and our detailed lensing-based mass maps will be uniquely powerful for that purpose. GALEX is sensitive to star formation on 10^7-10^8 yrs, making it ideal for probing the timescale of star formation quenching. This timescale is sensitive to the physical process that caused the quenching, for example ram pressure stripping or more gentle (slower) starvation. Structural analysis of the lensing mass maps will diagnose the the amount and location of recent hierarchical infall into the clusters. We will therefore be able to quantify cluster-by-cluster the timescale of quenching, to delineate how that quenching relates to hierarchical assembly and thus to pinpoint the physical processes responsible for quenching as a function of dynamical state of the clusters. Our results will therefore have a major impact on efforts to udnerstand how spiral galaxies transform into S0's. For this huge statistical survey, we request a modest 30 hours of observing time."
“GALEX surveys contain the most comprehensive collection of UV imaged extended galaxies likely to exist for decades. Unfortunately, with the exception of the 1,000 galaxies contained in the Nearby Galaxy Atlas (NGA), this impressive resource is under-utilized because 1) the pipeline-generated source catalogs split extended objects into many pieces (""shredding"") and 2) co-adding of data using multiple survey types is not regularly performed. We propose to solve both of these problems by constructing the GALEX Large Galaxy Atlas (GLGA) using all observations of galaxies with diameters of at least 1 arcmin, make it available to the public via the NASA/IPAC Extragalactic Database (NED), and provide our software for the co-adding and mosaicing of GALEX data to the astronomical community. The GLGA will build upon and extend the NGA in three significant ways; it will 1) contain 21,000 galaxies, 2) co-add data from multiple survey types, and 3) preserve multi-epoch observations to facilitate time domain studies. Extending the NGA to 21,000 galaxies will be a major contribution to the legacy of GALEX. Although the GLGA will be a tremendous resource available to anyone, our team was inspired to its construction for several projects. We will use the GLGA to measure proper UV-optical-NIR colors for a large sample of extended galaxies for the first time. This is a critical step for locating examples of nearby ``green-valley"" or transition galaxies which may be the best objects for understanding blue-red sequence evolution. We are compiling a matching catalog of HI single dish fluxes and images with the goal of using it to study the detailed relationship between gas content and star formation rate, implications for star formation ``laws'' and the triggering and quenching of star formation. Finally, we are compiling IRAS HiRes data for objects with diameters >2 arcmin with the objective of constraining UV extinction derived from the UV spectral-slope/infrared-excess correlation."
“The post-AGB star HD44179 and the surrounding Red Rectangle nebula exhibit several unusual spectroscopic anomalies. In the UV, HD 44179 shows strong absorption and emission bands of the 4th Positive system of carbon monoxide, and is the only known source of Cameron band emission (near 2000 A) outside the solar system. In the optical, the biconical Red Rectangle nebula is the strongest known source of Extended Red Emission (ERE), a broad hump of emission from 5000-9000 A. Although the ERE is ubiquitous (albeit weak) in many astronomical sources, and a significant contributor to the diffuse galactic background light at optical wavelengths, its carrier has not been identified. The presence of UV Cameron band emission in HD 44179 is particularly intriguing. The complete lack of other emission of comparable excitation (at about 6 eV) implies an noncollisional source. One possibility is a purely radiative mechanism involving an excitation loop via the 4th Positive bands, various excited triplet terms, and radiative decay in the (spin forbidden) Cameron bands. An attractive feature of this mechanism is that the CO triplet system decay produces emission in the red part of the spectrum, exactly where the ERE is observed. Indeed it is possible that all three spectroscopic anomalies seen in HD 44179 arise from the CO molecule --- a very satisfying prospect, and a hypothesis testable by means of UV imaging of the Red Rectangle nebula. The biconical nebular structure only appears in the ERE and not in the nebular scattered light. If the proposed CO radiative loop excitation mechanism is correct, then UV images of the nebula should also show the Red Rectangle biconical structure. Therefore we propose to image the Red Rectangle in the NUV and FUV with GALEX. If the anticipated biconical structure is observed, we will follow up with spectroscopic (GALEX grism) observations in Cycle 5."
“The objective of this proposal is simple --- to complete our ongoing Cycle 1 approved GALEX Legacy program, the 11 Mpc H-alpha and Ultraviolet Galaxy Survey (11HUGS). 11HUGS provides the most complete inventory of recent star formation in the Local Volume to date, and its scientific scope and archival value have been augmented with the recent approval of a companion Spitzer Legacy proposal to obtain IRAC and MIPS infrared imaging for the sample. Here, we request supplemental time with GALEX to achieve the highest completeness possible (as bounded by the facility's current safety brightness restrictions) for the UV component of the survey. We propose to take full advantage of both the relaxed safety limits (relative to Cycle 1), and the release of unobserved Local Volume targets which were previously reserved by the GALEX PI team, in order to recover sufficiently deep UV observations for 53 galaxies in 51 fields. The new observations will significantly improve the UV coverage of the sample from the current 77% (198/258) to 97% (251/258). The core PI science of 11HUGS was predicated on highly complete observations of a volume-limited sample, so achieving the most comprehensive UV coverage possible is necessary to ensure the statistical robustness of the star formation distributions and temporal properties derived. The imaging requested will also be crucial in securing the archival value of the overall multi-wavelength Legacy dataset, and finally, will bring closure to our systematic observational census of our nearest star-forming neighbors."
“We request new GALEX imaging with both the NUV and FUV detectors, for a mosiac of four pointings in the core of the Shapley Supercluster. The science aims are to assess the use of NUV-vs-IR colours as a tracer of stellar population age and metallicity, through comparison to a high-quality well-calibrated spectroscopic database. The UV imaging will complement existing ESO 2.2m imaging at B and R and wide-field K-band imaging with UKIRT/WFCAM. High-precision ages and metal abundances for ~250 galaxies have been determined from long-exposure spectroscopy with AAT/AAOmega. The FUV data are essential to remove empirically the contribution from the hot UV-upturn population. Our previous observations from GI1-004 covered part of the region requested here, but no FUV data was obtained."
“We propose deep far and near-UV images of 15 Galactic globular clusters (GCs) as a follow up to programs by our group in Cycles 1 and 3. The final database will be the largest homogeneous dataset ever produced on the UV photometric properties of Galactic GCs and will allow a full characterization of their hot stellar contents. Image size and resolution are such that excellent photometry outside the cluster cores can be obtained for statistically representative samples of all stars that contribute relevantly to the integrated light of stellar populations in the UV. These data will be used to address the following problems: 1) a study of the UV morphology of the horizontal branch, in order to shed new light on the late stage of evolution of low-mass stars, in connection with UV-excess of early-type galaxies; 2) constraining the models for blue straggler formation from studies of the radial distribution of these objects (in combination with HST photometry of the cluster cores, obtained by our own group); 3) enlarging the sample of known post-AGB and supra-HB stars by a factor of three, bringing a major boost to the statistics of these short-lived, yet UV-relevant stars; 4) Studies of integrated UV/optical colors of Galactic GCs, in order to study correlations of these integrated properties with global and structural parameters such as mass, concentration, core morphology, luminosity, age, and chemical composition. These data will provide important constraints on evolutionary models for stars and galaxies and will help to shed new light on the problem of the UV-excess of early-type galaxies. It will also serve as badly needed local templates against which data for distant, unresolved systems need to be contrasted."