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View an Abstract from CYCLE 2
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Proposal 1: The activity rate of dMe flare stars in the Hyades Open Cluster
We shall perform extended pointed observations of 2 regions of the Hyades open cluster to observe UV flare activity on dMe field stars. We expect to detect significant UV activity from at least 20 of these stars in each field, such that we can perform a statistical analysis of the typical time-scales and amplitudes of the observed emission variability. M-type stars are the most ubiquitous class of stellar object in our galaxy and they exhibit chromospheric and transition region behavior that is similar to our Sun, albeit with a far higher level of magnetic activity. These GALEX obsevrations will provide an important data-base of extreme solar-like activity recorded with an unprecedented time-resolution of < 0.1 seconds.
Proposal 7: Diffuse UV Background - GALEX Imaging and Voyager Spectroscopy
We propose a LEGACY project, with the aim of characterizing the diffuse ultraviolet background radiation. In order to achieve maximum impact, we propose to observe exclusively targets for which we already have in hand Voyager diffuse background spectra shortward of Lyman alpha. Our Voyager spectroscopy will allow powerful insight into the interpretation and meaning of the deep GALEX images (longward of Lyman alpha) that we propose (here) to obtain. There is good evidence that a substantial portion of the diffuse UV background at moderate and high Galactic latitudes is exotic in its origin---that is, that the radiation is not simply diffuse galactic light plus the integrated light of distant galaxies. We propose to find clues to the nature and physical origin of the diffuse ultraviolet background radiation in as comprehensive a manner as can be accomplished using GALEX. But in the course of carrying out the proposed work, we will also be creating a permanent GALEX archive of well-chosen deep images that are supported by spectroscopy---images valuable for a wide range of purposes beyond those that we propose. To speed this broader use, we waive all data rights. We successfully proved the feasibility and concept with a few exploratory pointings in Cycle 1, which support our current request for a comprehensive (Legacy) program.
Proposal 10: The second GALEX ultraviolet variability (GUVV) catalog
We shall implement our specialized software tools to serendipitously search the GR2 data archive for transient and variable UV stellar sources. Our aim is to detect and assign probable identifications and positions for these sources for inclusion in version 2.0 of the GALEX UV Variability (GUVV) catalog. Such sources will include dMe flare stars, cataclysmic variables, soft X-ray transients and intrinsically variable stars such as RR Lyraes and delta Scutis. This work supports the NASA strategic objective of understanding stellar structure and evolution.
Proposal 12: Hydrogen shell burning in close binary white dwarfs of the Local Group
I propose to study white dwarfs that are accreting and burning hydrogen in a shell in a close binary system, and are possible progenitors of type Ia SN, using all the Local Group images available at the time the project is done. First of all, I will search strong UV counterparts in the spatial eror box of ~60 supersoft X-ray sources observed in M31 at various epochs. Initial tests show that a bright UV counterpart is found in the error circle about half of the time. I will thus obtain quite precise positions for all those sources that were not observed with Chandra, and I will measure the UV flux and correlate it with the X-rays and optical fluxes or their upper limits, in order to constrain the theories. At least 5-10% of the sources are expected to have ionized the ISM up to parsecs away, and the extended nebulae should be detectable. I will also search strong FUV sources without known counterparts at other wavelengths in other Local Group galaxies, to plan new X-ray observations of these candidate supersoft X-ray sources. Finally, I will search the UV counterparts at the position of ~100 novae that exploded in M31 in the last 50 years, and of novae in other Local Group galaxies, to determine how long hydrogen burning lasts after the outbursts.
Proposal 15: Seeing Double in the Local Group: A GALEX Archival Study of Extragalactic Eclipsing Binaries
undamental properties and distances of selected hot eclipsing binaries (EBs) in Local Group galaxies (see Guinan 2004). One of the major results of this program has been the accurate determination of the distance to the Large Magellanic Cloud. We are proposing to use archival GALEX FUV (1530A) and NUV (2310A) images of the Large and Small Magellanic Clouds (LMC and SMC), M31, and M33 fields that contain thousands of newly discovered EBs. We plan to combine the GALEX FUV and NUV photometry with existing V, R, I (and in most cases B) photometry of these extragalactic EBs that will permit the determination of reliable temperatures and ISM absorption values for EBs with significant UV fluxes -i.e EBs with O- to late B-type stars. Also for the LMC and SMC, we will use available 2MASS J and K photometry. Extending the wavelength baseline to the FUV vastly improves the determination of T_eff and ISM absorption. Over 6500+ EBs have been serendipitously discovered in the LMC and SMC from the MACHO and OGLE microlensing programs. Well-covered V, R, or I light curves (as well as orbital periods and accurate positions) are available for these 14th-18th mag EBs. Also, several hundred EBs have been discovered in the giant spiral galaxies M31 and M33 and many have well-defined light curves, excellent orbital periods and positions. BVR photometry of the 19th-20th mag (mostly O-B) EBs in M31 and M33 are being carried out as part of the DIRECT program and by us using the 2.5m INT in the Canary Islands. In addition, ~100 EBs have been uncovered in several Irregular and Dwarf Spheroidal Local Group galaxies that include Leo I, Carina, Sextans, NGC 6822 and the nearby interacting Sgr Dwarf Spheroidal Galaxy (see Guinan 2004). This sample of galaxies represents a wide range of morphologies, chemical abundances (1-100th solar), star formation rates, dynamical conditions and stellar populations. Studying EBs in these galaxies will provide important ''laboratories'' for testing the effects of metal abundance and galactic environment on stellar structure and evolution. Also, the study of a large sample of extragalactic EBs will provide information about the star formation rates and gradients of the host galaxies. Utilizing procedures that we have developed over the last decade, we will combine the values of T_eff and ISM absorption (E(B-V)) data determined from the GALEX data with the astrophysical and orbital information determined from the analyses of the light curves and the available (or planned) spectroscopic radial velocity data. This study will yield fundamental astrophysical information and statistics for hundreds of EBs whose host galaxies have a wide range of metal abundances, stellar populations, star formation rates, and dynamical conditions.
Proposal 17: GALEX Follow-up on the Nature of A Dark HI Cloud in the Virgo Cluster
We propose an exploratory investigation on the nature of a potentially ``hidden'' galaxy in the Virgo cluster revealed in recent deep HI observations. Existing GALEX observations of nearby galaxies in UV have demonstrated the exciting and unique capability of probing regions of young stellar population far away from the main galaxy body, and extremely faint or undetectable in the visible wavelength. The higher spatial resolution of GALEX images comparing to the HI map will allow a much better assessment of the materials contributing to the enhanced HI column density in this seemingly empty region on the outskirt of Virgo; While a comparison with other nearby galaxies and tidal tails can help further explain why conventional star formations have been suppressed. In a broader sense, this observation can be a pilot effort leading to our better understanding of the dark matter on galactic scale.
Proposal 19: Jet ISM Interactions in Active Galaxies Nuclei
In a significant fraction of active galaxies, observations suggests a link between the radio jet activity and the host galaxy's global properties. Extended emission is seen in existing optical and X-ray data, and demonstrates that the ionizing effects of the radio components can extend far from the jet. The emission arises either from direct interaction with the radio plasma, or by radiative shocks. Theoretical models predict that radiative shocks can give rise to emission-line gas with extended, complex morphologies. They arise at the interface between the hot, thin ``cocoon'' surrounding the radio jet and the cool ambient ISM, and at the boundary layer that forms when over-pressured gas from the radio jet expands into the surrounding ISM. We propose to obtain GALEX UV imaging of the hot gas in a complete sample of radio galaxies with $z<0.03$. The morphology of the UV emission and it's relationship to the radio and X-ray will provide information about the excitation mechanisms. Shock excited gas is expected to have a strong UV component resulting from emission in the high ionization lines, such as C~IV. Theoretical models will be used to assess the relative contributions of shock excitation and photoionization in the hot UV emitting gas.
Proposal 20: Magnetic Fields on "Alien Dwarfs": Stellar Activity in the Arcturus Moving Group
The Arcturus Moving Group is very likely a remnant of the merger of a dwarf galaxy with the Milky Way Galaxy in the distant (7-8 Gyr) past. This kinematically distinct group has members that are located very close to the Sun, allowing study of stellar magnetic activity on very old stars that typically would not be possible. We propose to use GALEX grism spectroscopy to study four dwarf members of the Arcturus Moving Group with the aim of determining their transition region (UV emission line) activity levels, and the effects of low metallicity on the transition region radiative losses. Our targets have metallicities of only 20% solar, spectral types F9 - G8, and are at distances less than 30 pc from the Sun. Our aim is to measure fluxes for the C IV 1548, 1550 A emission lines, which are the strongest diagnostic of the radiative losses from the 10e5 K transition region, and the NUV/FUV continuum spectrum. The measured optical chromospheric Ca II emission levels of all four targets are comparable or higher than that of the quiet Sun.
Proposal 23: Accretion Rates of Recurrent Novae
We propose to use GALEX NUV and FUV grism spectra plus the ANDICAM on the SMARTS 1.3m telescope at Cerro Tololo to measure the spectral energy distribution for four recurrent novae (U Sco, T Pyx, RS Oph, and T CrB) from 1400-22000 Angstroms. The integral under this distribution (when light from the companion star is subtracted and the remainder is fitted to an accretion disk model) will give the accretion luminosity and then a mass accretion rate for each star. These accretion rates will be used in two ways to provide a strong test of the popular idea that recurrent novae are the primary progenitors of Type Ia supernovae. (This 40-year old problem has recently come to the forefront since the identity of the progenitor must be know to allow for calculations of the evolution of supernova peak luminosities and hence to allow NASA spacecraft, such as HST, SNAP, and JWST, to keep their promise of precision cosmology.) The first test is to combine the measured accretion rate with the observed recurrence time scale to see whether the mass accreted between eruptions is greater or less than the mass ejected during the eruption (as measured by the orbital period change across the eruption). If the white dwarf is gaining mass each eruption, then it must inevitably collapse as a Type Ia event. The second test is to combine the accretion rate with the derived number of recurrent novae in our Local Group so as to get a recurrent nova death rate, and then compare this with the Type Ia event rate. If the recurrent nova death rate is nearly equal to the supernova rate, then the recurrent novae are likely the dominant progenitor.
Proposal 24: GALEX Imaging Study of the HI Filaments in M81 Group
We propose to obtain sensitive, wide-field GALEX NUV and FUV images of the area surrounding the central four main members of the M81 group (M81, M82, NGC~2976, NGC~3077) as an integral part of our multi-wavelength observational program to explore the star formation activity, associated radiation field, and details of galaxy evolution/transformation within the group. We will add two pointings adjacent to the Cy-1 program pointing of the M81-M82 field by Huchra et al. (GI1-071) to the same depth (sufficient to detect star formation activity expected for a mean HI column density of a few times 10^18 per cm^2 with S/N>5) to cover most of the 3 degree diameter region we have imaged in 21cm HI line using the VLA, DRAO, and GBT. By combining with our imaging data from IR (Spitzer Cy-2), optical/IR (SDSS, 2MASS), and CO (FCRAO) surveys, we will conduct an extensive quantitative analysis on the distribution of cold gas and dust and star formation activity traced in UV and IR associated with the extensive array of HI tidal streamers. Because of its proximity, M81 group is one of the few extragalactic systems where such analysis can be made at spatial resolution of 100 pc or better. The high quality HI, CO, and dust maps (plus the dyanmical models for the group interactions) make this group an exceptional laboratory for determining the star formation and tidal dwarf formation process.
Proposal 25: The Origin of the Warm Hot Intergalactic Medium and Its Relationship to Galaxies
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 five well-studied QSO sight lines having low-redshift ionized oxygen (OVI) and broad H I Lyman-alpha lines, both of which are excellent tracers of hot gas with log T(K) = 5-6. We will: [1] Derive the UV colors and correlate the star-formation properties of the galaxies at the redshifts of the absorption-line systems with the absorber properties (hot gas content,metal content, line widths, etc) and sight line impact parameters.[2] Compare the star-formation results with galaxy morphology as derived from both ground-based images and archival HST/WFPC2 data.[3] 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 sheets and filaments in the cosmic web. The galaxies and absorbers to be studied are in the ideal redshift range for investigations of galaxy-absorber relationships (z ~ 0.01-0.4) since the sight lines are long enough to contain intergalactic absorption features, yet the absorbers and galaxies are near enough to be able to study the individual components of galaxy-IGM systems. The results of this study will better define the distribution of metals outside galaxies, the evolution of galaxies in proximity to intergalactic gas, and the importance of galactic feedback processes on the morphology of the cosmic web.
Proposal 26: New Search for Subdwarf B Stars from the GALEX
We propose to carry out medium-resolution spectroscopic follow-up (1) for the identificaiton of \textit{bona fide} subdwarf B (sdB) stars from the \emph{new} set of sdB star candidates chosen from the GALEX photometry in the GR2, in combination with other optical and near IR photometry, and (2) for the radial velocity variability monitoring for sdB stars identified from our previous and current efforts in order to determine the binary fraction of sdB stars. The UV bright, hot sdB stars are considered to be core helium-burning stars of 0.5 $M_{\odot}$ with very thin hydrogen envelopes of $M_{\mathrm{env}} \le 0.02 M_{\odot}$, and immediate progenitors of white dwarfs. Although their current and post evolutionary status is relatively well understood, very little physics behind their formation/evolution is known. For instance, it is not clear whether such stars are born as single stars or can form only in binary systems. The number ratio of sdB stars in each Galactic stellar population (i.e., thin disk, thick disk, and halo) may give a clue to answer whether major formation mechanism can be explained by binary scenario or RGB peel-off scheme (Altmann et al. 2004, A\&A, 414, 181). This approach was hampered by lack of identified sdB stars belonging to thin disk and halo. Thus, of primarily importance is new detection of sdB stars with faint magnitudes (halo) and at lower Galactic latitudes (thin disk). The huge data set of GALEX sdB stars, which reach the entire UV visible Milky Way, will eventually answer most of the remaining questions associated with their formation and evolution mechanism, and Galactic structure.
Proposal 27: New Search for Very Metal-Poor Stars with [Fe/H] < -2.0 from the GALEX
The old, and most metal-poor stars in the halo and thick disk of the Galaxy provide vital clues for unraveling the structure, kinematics, and chemical composition of the early Milky Way. There have been a few successful anaylses of chemical abundances and dynamical motions of such stars, but the spatial scales have mostly been limited to include only a few kpc from the Sun since most of them are dwarfs and sub-giants near the main-sequence turnoff. Metal-deficient red giant stars are ideal probes of both the inner and outer halo, since they are intrinsically luminous, and thus more distant. We propose to carry out (1) medium-resolution spectroscopic follow-up for the identificaiton of \textit{bona fide} very metal-poor (VMP) red giant stars with [Fe/H] $< -2.0$ from the \emph{new} set of VMP star candidates chosen from the GALEX photometry in the GR2, in combination with other optical and near IR photometry, and (2) subsequent high-resolution spectroscopic follow-up of comprehensive abundance analyses for VMP red giant stars identified from previous step. From this effort, we expect to \emph{newly} reveal a few thousand \textit{bona fide} VMP stars over a range of depths and sky-coverages. Indeed, this huge data set of GALEX VMP stars will help unravel the early nucleosynthesis, stellar dynamics, and substructure of the Galaxy.
Proposal 32: A GALEX Archival Search for Young Solar-type Stars
We propose to expand our successful archival study of the GALEX All Sky Imaging Survey to search for young (< 100 Myr) stars in the solar neighborhood. Ordinarily such stars are difficult to identify against the backdrop of field stars since they have dispersed from the parental molecular clouds and no longer possess distinguishing optical and near-infrared photometric characteristics. GALEX offsets a unique opportunity to find young stars in the field via ubiquitous UV-excess emission caused by enhanced chromospheric activity relative to Pleiades-aged and older stars. By combining GALEX data with the Tycho and 2MASS databases, we can efficiently construct candidate lists of young stars and then obtain follow-up optical spectra to establish youth. Finding these stars is essential since theoretical and observational considerations suggest that planets of all masses are in their final assemblage stages between ages of ~3 and 30 Myr. Thus, constructing respectable samples of stars in this age range is a necessary and essential step for empirical measurement of the evolution of circumstellar disks during the epoch of giant and terrestrial planet formation. We demonstrate the feasibility of our technique by cross-matching the GALEX Cycle 1 data release (containing 10% of the sky) with 2MASS. A number of candidate young stars are identified, including the ``rediscovery'' of the nearby star AU Mic and a 140 Myr old cluster. These results indicate that GALEX can detect AU Mic-like objects out to distances of 100 pc and TW Hydra-like objects out to 240 pc. Follow-up optical spectroscopy of the UV-excess sources are underway that will identify the young stars in our candidate list. Given the promising results thus far, we propose to expand this study to the additional 23% of the All Sky Imaging Survey that will be released in Cycle 2. Our program will provide a lasting legacy to the GALEX mission by producing a catalog of nearby young stars.
Proposal 33: A GALEX Imaging Survey of M31's Halo
We propose to perform a wide area imaging survey of M31, the Andromeda Galaxy, with the GALEX observatory. The principal goal of this survey is to identify bright UV sources using the unique imaging capabilities of GALEX. With follow-up ultraviolet spectroscopy, these sources will allow us to study the temperature, extent, and composition of the halo gas of M31. Used in conjuction with the wealth of existing/proposed panchromatic data in this region, our proposed GALEX images will have tremendous treasury value for studying M31's halo and satellite stellar populations. This program is well matched to several of the core science goals of the GALEX mission. These include studies of star formation, galactic structure, and diffuse ionized gas. Within the NASA umbrella, this proposal is best related to the former ORIGINS division, i.e. the growth of the universe from cosmic seeds.
Proposal 34: Star Formation and Molecular Gas in Massive Low Surface Brightness Galaxies
Massive low surface brightness (MLSB) galaxies have disk central surface brightnesses at least one magnitude fainter than that of the night sky, but total magnitudes and masses that show they are among the largest galaxies known. Recent work has clarified the structural parameters and stellar and gas content of these enigmatic systems, yet our understanding of the star formation process within MLSB galaxies is still poor. To advance our understanding of these objects, we propose to obtain GALEX NUV and FUV images of eight MLSB galaxies whose molecular gas content has already been quantified. The GALEX images will be combined with our optical, HI, and CO data, enabling the most in-depth study to date of how, when, and where star formation proceeds in this unique and important subset of the disk galaxy population.
Proposal 35: Star Formation History in the Richest Clusters of Galaxies
We will observe six of the richest Abell clusters in order to determine the star formation histories of their member galaxies. Recent radio studies indicate that the star formation and evolution of cluster galaxies is intimately tied to cluster dynamical state. Our targets were selected by combining our sensitive radio continuum survey of clusters with the SDSS, thereby providing quality imaging and spectroscopic data of hundreds of cluster members. The optical data will be used to determine the kinematics of the clusters, which on the basis of X-ray morphology are separated into three dynamical states: 1) virialized clusters, 2) substructure clusters (including major merger events), and 3) ''protoclusters.'' The importance of the GALEX data is that they will provide a unique look at star formation over 10^9 year timescales, which is the same time range where models for galaxy evolution in the cluster environment predict the most transformation. The excellent sensitivity of GALEX to recent star formation will also extend the radio results down to much lower levels of activity, providing large numbers of objects for use in statistical comparisons among the clusters. Finally, the wide field of view of GALEX will explore activity from the cluster cores out to well past the infall regions. The end goal is a more detailed understanding of the relationship between cluster dynamical state and the evolution of member galaxies.
Proposal 36: Robust Object Classification in a GALEX-SDSS Federated Dataset
We propose to improve our classification of every photometric object in the Sloan Digital Sky Survey using the UV data from GALEX GR1 and subsequent data releases. In collaboration with domain experts at NCSA we have produced a catalog of classified objects with photometric redshifts in the SDSS Data Release 3 using advanced machine learning algorithms. The catalog has several unique features, including an unprecedentedly large and complete sample of quasars generated without the use of explicit color or luminosity restrictions. We propose to extend this catalog using the UV bands, taking advantage of the large areal overlap between GALEX and the SDSS. The addition of the UV bands to our catalog will increase the completeness, decrease the contamination, and significantly improve the accuracy of our photometric redshift estimates. For example, in the {\em optical redshift desert}, the Lyman break in the GALEX-SDSS UV colors cleanly allows us to estimate redshifts. The scientific capabilities of our federated GALEX-SDSS catalog are immense; and our catalog, will, therefore, become a valuable community asset. As a result, we will publicly release the full catalog once it is scientifically verified. The relevance to NASA goals is the exploration of the structure and evolution of the universe.
Proposal 37: GALEX Identification of a Large Sample of New Quasar Sightlines for the Study of Intergalactic Helium
The reionization of intergalactic helium is often argued to have occurred between redshifts of about 3-4. Previous studies of HeII Lyman-alpha absorption toward a half-dozen quasars at z>2.7 have demonstrated the great potential of such probes of the IGM, but the current critically-small sample size limits confidence in resulting cosmological inferences. The requisite unobscured quasar sightlines to high-redshift are extremely rare, but SDSS provides thousands of new quasars that are potentially suitable for HeII studies. In our GALEX cycle 1 archival program, we've combined GALEX GR1 and SDSS DR3 data on 330 SDSS quasars to identify more than a dozen new unobscured UV-sightlines to high-redshift, i.e., those best-suited for HeII studies. We propose to greatly extend our sample via expanded GALEX GR2 and SDSS sky coverage, surveying UV emission from about 1350 additional high-redshift quasars. Along with our cycle 1 work, this expanded GALEX GR2 sample should yield nearly 10^2 new unobscured SDSS quasar UV sightlines to high-redshift. Such an unprecedented large sample of clean UV-sightlines will enable future, statistical, follow-on HeII studies that constrain the spectrum and evolution of the ionizing background radiation, establish the epoch of IGM reionization, and measure the density of intergalactic baryons.
Proposal 38: Ultraviolet Spectroscopy of Recent Classical Novae
Novae are important contributors to galactic chemical enrichment on local scales. Spectroscopy of novae provides information about the elemental abundances of the gas in the ejecta dispersing into the interstellar medium (ISM) as well as kinematic information related to the outburst. We propose GALEX grism observations of two recent classical novae. The ultraviolet spectra, combined with optical, near-infrared, Chandra X-ray, and mid-infrared Spitzer spectra, are critical to determining accurate abundances of nova ejecta. These abundances will help to determine the importance of nova contributions to the ISM and, in particular, the roll that novae play in the abundances of certain intermediate mass elements and their nucleosynthesis which is observed in the ISM and meteorites. We also get the densities and ejected masses which could provide insight on the supernova Ia progenitors.
Proposal 40: The Star Formation Rate in a Nearby Damped Lyman-alpha Absorber
We wish to obtain deep GALEX images of the intervening Low Surface Brightness (LSB) galaxy SBS 1543+593 (z=0.009) which lies in front of the background QSO HS 1543+5921 (z=0.807). A detailed analysis of the CII* absorption line from the LSB galaxy in the background QSO spectrum has enabled us to calculate the star formation rate (SFR) along the sightline. To validate our results, we wish to use GALEX to measure directly the SFR in the galaxy. This is an important test, since CII* absorption lines are currently being used to quantify the SFRs in the population of high-redshift Damped Lyman-alpha (DLA) absorbers. Although this method is likely to be an important diagnostic of the physical conditions in these systems, the high-z of the DLAs makes it extremely difficult to test whether the absorption line data is giving the correct answer for the SFRs. We know, however, that SBS 1543+593 is itself a DLA, and its low-z means that the SFR can be measured directly with GALEX, allowing us to compare the real SFR with our inferred value. The LSB is also interesting in its own right: the optical emission is embedded in an HI disk with a radius ~10 times that defined by the starlight. GALEX data would enable us to search for low rates of star formation in these outer regions, as well as isolated stellar complexes, offering important insights into the star formation history of the galaxy. SBS 1543+593 also appears to be part of a galaxy group, which raises the problem of how the large HI disk has managed to survive in such a potentially destructive environment. Since GALEX is adept at revealing low surface brightness features such as tidal tails, our data would allow us to search for clues as to how the LSB galaxy is interacting with its environment.
Proposal 41: An Archival Study of Hot Stars in Galactic Globular Clusters
We propose an archival study of GALEX ultraviolet imagery of 23 Galactic Globular clusters. Ultraviolet imagery suppresses the dominant cool star population of a globular cluster, revealing the hot horizontal branch (HB) stars and post-asymptotic giant branch (post-AGB) stars. Using these data, we will address three major science goals. First, the GALEX images should provide complete samples of the hot post-AGB populations in the observed clusters, as well as important constraints on the lifetime and luminosity of this poorly studied phase of stellar evolution. Second, the GALEX images should provide improved number counts for the hot post-HB stars, which can then be used to test theoretical lifetimes, and to constrain the helium abundance from the size of the luminosity gap between the hot HB and post-HB phases. Third, because the bolometric correction is relatively small for hot stars in the GALEX bandpasses, it will be possible to study the bolometric luminosity distribution along the hot HB, and hence to search for the effects of an enhanced helium abundance. These data will permit a crucial test of the helium pollution scenario of D'Antona et al. (2002) for explaining the formation of extended blue HB tails (one aspect of the ''second-parameter'' problem), and the abundance anomalies observed in red giant and main-sequence stars.
Proposal 44: Finding the Edge of the Disk: Star Formation at Large Radii
We propose to obtain very deep FUV and NUV imaging observations of a sample of five spiral galaxies chosen specifically to characterize star formation in the outer disk. These galaxies all have average HI extents (from VLA observations) and exceptionally deep H alpha observations have provided a complete census of recent massive star formation. In all cases, there is some star formation beyond the optical radius. The proposed FUV and NUV images will be compared with these H alpha images to examine possible IMF variations in the outer star forming regions. In addition, the sites of active star formation will be compared with existing spatially resolved neutral hydrogen data to investigate theoretical models of the onset and propagation of star formation activity in low density environments.
Proposal 46: Constraining low-level star formation activity: A Deep GALEX survey at the outskirts of the Coma Cluster
We propose moderately deep 30ks NUV and FUV observations of a field in the outskirts of the nearby, rich Coma cluster to study the star-forming properties of galaxies down to very low stellar masses. NUV and FUV coverage with GALEX will provide critical information on the age of the stellar populations in galaxies as well as providing a critical additional constraint on dust reddening. We have chosen the particular field, which is more than 40 arcminutes from the cluster center, due to its superb multiwavelength coverage. This coverage includes optical spectroscopy providing measurements of metallicity and current star formation, near-infrared (K-band) imaging which gives stellar mass estimates, mid-infrared imaging for precise characterization of the old stellar component, and X-ray data which probe the obscured accreting binary populations and hot gas in galaxies. We will test recent results that show a tight correlation exists between past star-formation and optical-UV color, UV surface brightness and specific SFR, and X-ray flux and SFR. This deep GALEX Coma survey is uniquely poised to make these investigations of very low mass dwarf galaxies. There has been a large body of work by the GALEX PI team in deep survey fields at higher redshifts, and of wider-field, moderate-depth fields at lower-redshift. This survey is different in that we observe the outskirts of a cluster where we know the local galaxy density is still significantly higher than the field (and thus we may efficiently observe a large number of galaxies at once, we anticipate hundreds of Coma-member detections in our chosen GALEX field). Our observational goal is to observe the most quiescent galaxies (elliptical-type SEDs) at the lowest masses (down to absolute R-band magnitudes of MR=-16). Recent GALEX results indicate that a useful observational goal is to observe down to NUV-R=5, which is found to be typical of fairly quiescent galaxies. This corresponds to an NUV magnitude of 24 at the distance of Coma for MR=-16, requiring 30 ks of observations. The additional FUV data will permit age constraints using FUV-NUV colors. Understanding the nature of the dwarf galaxy population, via characterization of the faint-end of the luminosity function, remains critically important in modern cosmology. A secondary goal of our program is to measure the SFR using many different multiwavelength techniques, with particular focus on testing the relatively recent X-ray/SFR correlation which affords the opportunity to test theories of accreting binary evolution.
Proposal 48: The PERSEUS Cluster in the Ultraviolet
A basic goal of the GALEX mission is to assess the effects of environment on galaxy evolution. The Perseus cluster of galaxies represents one of the most extreme environments in the local universe and features a spectacular mix of astrophysical phenomena. It is the nearest rich cluster and contains a massive, hot, X-ray bright intracluster medium. Its central dominant galaxy, NGC 1275, is remarkable for its luminosity; its powerful radio source; evidence for extensive recent star formation, some induced in the intracluster gas by the radio source; and an enormous ($r \sim 60$ kpc) system of emission line gaseous filaments. In Cycle 1, we successfully obtained beautiful, deep (15 ksec) images of Perseus with GALEX. We detect FUV-bright filaments around NGC 1275, many of the E/S0 galaxies, and bright FUV emission from a number of the peculiar late-type galaxies. Here, we propose deep GALEX grism spectroscopy of this same field. We will use the leverage afforded by UV spectroscopy to study the ``UV-upturn'' in old populations of E/S0 galaxies, the nature of the NGC 1275 filaments, and the character of star formation in the late-type systems in this unique cluster.
Proposal 53: A Study of the Winds in Be Stars in the Magellanic Clouds
We propose GALEX/grism spectroscopy of two fields in the Magellanic Clouds to investigate the wind mass loss in Be stars that reside in a metal-deficient environment. Although more than 250 Be stars have been identified in the Magellanic Clouds, very little is known about the nature of their mass loss or how it compares with galactic Be stars. The project will provide information on whether the wind mass loss scales with the mean abundances in the Magellanic Clouds. If it doesn't, then we can rule out the radiation field as the main driver of the mass loss and look toward other mechanisms such as magnetic fields or nonradial pulsations. The clusters chosen for study are NGC 1818 in the LMC and NGC 330 in the SMC. Grism images will be obtained during four separate spacecraft orbits to achieve a S/N ~20-100 for all stars earlier than ~B2.5. The C IV (1550 A) and Si IV(1400 A) wind and photospheric lines are expected to be prominent in the grism spectra of the early B stars. The project will also address the question of the percentage of Be stars relative to their early B non-emission counterparts in the Magellanic Clouds. New candidate Be stars will be identified in each cluster and its nearby field. The relative population of Be/(B + Be) stars will be compared with the results from ground-based studies by Maeder et al. (1999) and Keller et al. (1999) who disagree on whether the fraction is generally larger in the Magellanic Clouds. The cluster/field fraction will provide a test for a recent conclusion by Fabregat & Torrejon (2000) that the Be phenomenon sets in as the stars approach the terminal age main sequence.
Proposal 57: GALEX Deep Observation of the Edge-on Spiral NGC 55
We propose to use GALEX to obtain deep images of the nearby edge-on spiral NGC 55. NGC 55 exhibits a considerable variety of outflows in H${\alpha}$ images, indicative of active SF regions. The recent discovery of dust in the outer regions of galaxies raises the possibility of differences in the dust vs. gas distributions. We will search for sub- structure in the halo emission. The deep observation will also serve to delineate more precisely the outer `edges' of this edge-on spiral, permitting a sensitive search for hot vertical plumes that signal a connection between halo and disk (eg, chimneys). We will also search for spatially- resolved correlations between the GALEX UV and Chandra X-ray emission arising from the star clusters visible along the plane. Several of the point sources detected in the X-ray band are variable, including two that lie well out of the galaxy's plane. GALEX observations will probe the varia- bility across a broad range of times.
Proposal 61: UV Spectroscopy of Nearby Supernovae - the Key to Understanding High-z Star and Galaxy Formation
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. Unfortunately, UV spectroscopy of local SNe of all types, which can only be obtained from space, is almost non-existent. Such UV data are also powerful probes of the SN environment, progenitor structure and explosion mechanism. Recognizing the great value inherent to UV spectroscopy of local SNe, the SN research community has come together, and proposed a large Cycle 13 HST program (PI Filippenko), now inprogress, to study in detail a single SN subtype, SN Ia, in the UV. We have been awarded 33 GALEX orbits during cycle 1 to attempt target-of-opportunity GALEX spectroscopic observations of nearby, bright non-Ia (core-collapse) SNe, complementing this large HST effort. Following the successful recent implementation of this pilot program, we request here similar spectroscopic observations for three additional SNe, leading towards a full characterization of the UV spectral evolution of SNe of all types.
Proposal 121: Present-Day Star Formation in Local Group Analogs
We plan to get GALEX deep, broad band imaging of several loose galaxy groups chosen to be analogs of our own Local Group (i.e. consisting of a few large spirals separated by a few hundred kiloparsecs). This will allow us to (i) verify whether already detected HI-rich members of these groups do host ongoing star formation processes, thus confirming they are indeed MC-like, UV-bright systems (ii) derive the ratio of these low-mass, star-forming systems to high-mass galaxies (both UV-bright in this kind of groups), an issue related to the so-called ''missing satellite'' problem (namely the deficit of luminous satellite galaxies compared to cold dark matter models of galaxy formation, as observed in the Local Group) (iii) get templates of our own Local Group as seen ''from outside'', potentially useful especially to better estimate typical, present-day star formations one should expect in it.
Proposal 125: UV observations of the Virgo cluster covered by the Arecibo Galactic Environment Survey
As part of the Arecibo extra-galactic ALFA survey consortium we are carrying out a fully sampled HI survey - the Arecibo Galactic Environment Survey or AGES. AGES is specifically designed to investigate various galactic environments to higher sensitivity, with better spatial, and velocity resolution than previous, fully sampled, 21 cm multi-beam surveys. We have chosen, among other regions, a 25 sq deg region of the Virgo cluster upon which to centre our observations, but will also use the full depth of the survey to quantify the HI properties of more distant galaxies. The selected region will be also surveyed in optical and near-IR bands. Given the tight association between the atomic gas, the primary feeder of star formation in galactic discs, and the UV emission, tracer of the ongoing star formation activity, the GALEX data are of paramount importance for us since they allow a direct study of the relationship between the gas and the star formation in the environment of a rich cluster. Given our HI mass and column density sensitivity we require deep UV observations (~1 orbit per field) to place significant limits to the UV emission from HI sources. Owing to the existence of other GALEX fields in the Virgo area already obtained in guaranteed and open time or programmed, only ~ 35 orbits are sufficient to fully cover the selected region.
Proposal 127: A GALEX Globular Cluster Deep Field: searching for the primordial CVs in 47 Tuc
We propose to carry out a deep far- and near-ultraviolet survey in 47 Tuc in order to study the hot stellar populations in this cluster. Our primary goal is to test predictions of primordial binary formation theories. In order to do this we will detect and study the distribution of CVs outside the cluster core. When combined with our existing HST survey of the cluster core, this will yield the first deep view of the CV population of a cluster as a whole. In addition, we will also detect and study the white dwarf population, search for UV counterparts to the CHANDRA sources detected in this cluster, study the UV properties and distribution of the blue straggler population within the cluster, study the population of blue horizontal branch stars that are located in the outskirts of the cluster, and search for variability among the detected FUV sources. We will achieve this with 35 orbits of combined FUV and NUV imaging. Since crowding is not a problem in the outside the cluster core, this will yield time-resolved FUV photometry of all blue objects in the cluster. This will be the deepest FUV survey of a complete globular cluster ever.
Proposal 141: GALEX UV Observations of the Hubble Deep Field South : Making use of a large Multi-lambda Database
We propose to observe the Hubble Deep Field South from GALEX photometric observations. Our team is involved in an effort to build a multi-wavelength database that contains two important data for our science goals : visible spectroscopy for the distance and HST imaging for the morphology. In brief, the objective is to compare, on the same ground i.e. two rest-frame UV-selected galaxy samples at low and high redshift with the maximum of multi-wavelength complementary data over the GALEX 1-deg2 field. Since the way galaxies are selected has a strong impact on the type of observed galaxies (e.g. Lyman Break Galaxies and Sub-mm Galaxies), the originality of this work is that both samples would have the same biases and any difference would be due to an intrisic evolution with time. From these samples, we will deduce galaxy physical parameters such as the star formation history, the dust attenuation, the mass and size of galaxies and try to understand the evolution (if any) between the two redshift range 0<z<1 and z>2 that we can compare to models. We already developed tools to study multi-wavelength (including UV) Spectral Energy Distributions.
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