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Proposal # 041 Young Stars in Old Galaxies: A UV Imaging Survey of the Sauron Galaxy Sample
Simultaneously constraining the dynamics and stellar populations of galaxies is essential to understand their mass assembly and star formation histories. The SAURON Team has surveyed the two dimensional stellar/ionized-gas kinematics and stellar populations of a representative sample of 72 nearby early-type galaxies. It revealed a great dynamical diversity, discovering numerous central disks and kinematically decoupled components. The limited optical line strength diagnostics indicate that most (but not all) galaxies have homogeneously old stellar populations. By combining GALEX far-ultraviolet (FUV) and near-ultraviolet (NUV) imaging with SAURON data, we aim here to more reliably constrain the incidence, rate, and spatial distribution of recent and ongoing star formation in early-type galaxies, and to quantify those as function of luminosity, Hubble type, and environment. Of particular interest is whether star formation is closely associated with the kinematic (sub-)structures detected. Other important goals include measuring the spatial extent of the enigmatic UV-upturn population, identifying the orbital families populated by young stars and onstraining their migration patterns, and testing the reliability and limitations of line strength-based methods to detect young populations. Progress toward those goals was achieved with Cycle 1 data, but we now request to complete the sample by observing galaxies originally planned for the GALEX Nearby Galaxies Survey (NGS). The combined SAURON and GALEX data will provide by far the best determination of the relative roles of merger-induced and passive star formation in early-type galaxies today, and they will give us a unique glimpse into the future of those objects.Proposal # 042 Stellar Activity in open Clusters
We shall perform extended pointed observations of two regions in the Pleiades open cluster to observe UV flux variability due to flare activity on M-type stars. Using newly developed software tools we shall be able to probe a more comprehensive range of level of magnetic activity on a wider range of spectral types than that presently achieved at X-ray wavelengths. Our observations will determine flare energies and activity levels as a function of spectral type for the 110 Myr old cluster that can be compared with similar data obtained in Cycle 2 from the older 600Myr old Hyades cluster. These data are of particular relevance to the determination of habitability zones around M-stars, which account for 80 percent of the stellar population in the Galaxy.Proposal # 045 Star Formation in the Outer Parts of Dwarf Galaxies: Archival Data
Dwarf irregular (dIm) galaxies serve as laboratories of star formation without the influence of spiral density waves or shear. They are also like the proposed building blocks of spiral galaxies in the cold dark matter theory. Thus, dIm galaxies are an important component of the universe. We have conducted a large multi-wavelength survey of relatively nearby dIm systems aimed at determining what regulates star formation in tiny galaxies. In this proposal we are requesting funding to use UV images of our survey galaxies in the GALEX archives to trace and characterize star formation in the outer parts of these galaxies where Halpha is no longer detectable. With the GALEX images we will measure star formation rates with radius, determine if the star formation activity follows breaks seen in stellar density profiles, determine whether the star forming units in the outer galaxy are similar in size and structure to those typical of the inner galaxy, and examine the relationship between star formation and gas structures in the outer parts of dIm systems. Examination of star formation properties in the realm of very low gas densities will be a crucial test of various star formation models.Proposal # 046 Stellar Populations and XUV Disks in Red- & Blue-Sequence E/S0s
We propose a NUV+FUV imaging survey of 30 E/S0 galaxies in a sample representative of the mass range below 10^11 Msun where many E/S0s have substantial gas. This mass range includes an abundant population of "blue-sequence" E/S0s, a recently identified galaxy class that shows signs of disk building and may provide long-sought observational evidence for evolution from early types back toward later types, as predicted by hierarchical galaxy formation. The wide field and sensitivity of GALEX will allow us to survey our sample of low-mass E/S0s for faint extended UV (XUV) disks, similar to those recently discovered for later-type systems in the GALEX Nearby Galaxy Survey. Such disks can extend to 4x the optical radius and may represent new disk growth. At all radii, GALEX FUVNUV colors will provide a sensitive tracer of young populations and an excellent clock for identifying stages of evolution up to a few 100 Myr. Combining the GALEX imaging with optical and Spitzer data available for the full sample, we will construct a spatially resolved picture of star formation and the mass in young and old stars, to determine whether any of our targets are experiencing significant morphological transformation.Proposal # 050 Tracing the Extreme Edges of Galaxies in UV and HI
One of the most surprising discoveries of the GALEX mission is without doubt the discovery of extended star formation disks in nearby galaxies. Detailed comparisons with new, high-sensitivity, high-resolution VLA HI data from "The HI Nearby Galaxy Survey" (THINGS), which are beautifully matched to GALEX in its spatial resolution (6"), provide strong evidence for a well defined Schmidt Law, with no lower bound, i.e. no star formation threshold (SFT), yet detected. Comparisons are limited by the GALEX data though (with exposure times of 1.5 ks per galaxy), but indicate that there is even more extended star formation occurring at progressively lower HI column densities. To investigate this phenomenon further, we have selected a sample of 8 galaxies spanning a diverse range of galaxy parameters. For those galaxies we are requesting UV exposures with an increased signal-to-noise ratio by a factor of 3 (an additional 12 ks per object), in order to be able to probe in a systematic way and for the first time a part of the UV parameter space investigated in only one other galaxy before (NGC 300). This will allow us to push the UV detection limit significantly below the canonical 5.6E20 per cm**2 HI column density SFT.Proposal # 061 Star Formation in Nearby Galaxies: Completing the ANGST and ANGRRR Samples
The ACS Nearby Galaxy Survey Treasury program (`ANGST') and the Archive of Nearby Galaxies: Reduce, Reuse, Recycle (`ANGRRR') are HST Treasury and Archival Legacy programs concentrating on a complete sample of galaxies within about 4 Mpc. Many of these galaxies have been observed by GALEX under the Nearby Galaxies Survey or the 11HUGS Survey. Here we are requesting GALEX observations of the ANGST and ANGRRR targets which do not have planned GALEX observations. By comparing the UV light distributions for these galaxies with the spatially and temporally resolved star formation histories derived from the HST observations, we can make a direct connection between the age and amplitude of the star formation and today's UV emission. The majority of the proposed galaxies are low luminosity, low metallicity galaxies which are particularly important for this type of work.Proposal # 062 Star-formation in low luminosity galaxies
Dwarf galaxies are simple relative to more luminous galaxies, ideal for testing predictions of cosmology, of star-formation in disks, and of the effect of environment on galaxy properties. To study dwarf galaxies, we have constructed a joint sample of optical, Spitzer, and HI data, including resolved long-slit spectroscopy, showing among other things that these galaxies have extremely low star formation efficiencies. We propose to add archival GALEX data to a joint analysis of dwarf galaxies' optical, infrared, and radio properties to determine their star-formation histories and to better understand galaxy formation in this regime. We will attempt to construct a consistent star-formation history explaining the colors, metallicities, gas contents, and current star-formation rates of dwarf galaxies, and to examine how these properties vary with environment.Proposal # 063 UV Photometry of RR Lyrae Stars
RR Lyrae stars are conspicuous and numerous amongst the variable stars discovered by GALEX. RR Lyrae UV light curves have been constructed using GALEX time-series photometry, and the resulting UV colors have been compared to Kurucz model atmospheres of differing metallicity throughout the light curve. The metallicity of none of these stars is known, so the fit to Kurucz models cannot be confirmed. We propose to observe three RRab stars with known metallicity (DX Del, SU Dra, and RR Cet) to confirm the UV application of Kurucz models to RR Lyrae light curves, and to investigate the UV colors of stars differing in [Fe/H] at a number of points on the light curve.Proposal # 067 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 modeling 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 focused on a single SN sub-type, SNe Ia ($\sim10$ objects observed), while data for SN of all other types (core-collapse events) is almost non-existent. We have been awarded a total of 66 GALEX orbits during cycles 1 and 2 to conduct target-of-opportunity GALEX spectroscopic observations of a single nearby, bright, core-collapse SN in each cycle. Following the successful implementation of our program, we request here similar spectroscopic observations for two additional SNe. The accumulated GALEX data on non-Ia events, combined with the results from past efforts using HST and IUE, is leading toward a full characterization of the UV spectral evolution of SNe of all types.Proposal # 070 Narrow Line AGN Beyond the Lyman Limit
We propose UV imaging of 3 fields containing 5 luminous narrow-line AGNs (AGN 2s, ranging in luminosity from Seyfert 2s to Type 2 quasars) at z > 1. The target redshifts are selected to shift the continuum blueward of the Lyman limit into one of the GALEX filters. This will more than double the existing wavelength coverage of any narrow-line AGN SEDs and, for the first time, determine the bolometric luminosity, ionizing continuum, and strength of the Lyman break. If the far- UV continuum is scattered light from a Seyfert 1 nucleus, it will show no Lyman break. If the UV continuum is from hot stars, it will be completely black beyond 912 angstroms. Detection of intrinsic partial Lyman edges would provide a rough estimate of how much UV light is stellar and how much is nonstellar. At these high z's, the shortest GALEX band pass is a pure measure of nonstellar light, uncontaminated by stars. We will also estimate the contribution of AGN 2s to the cosmic UV background. Several suitable targets need to be observed to avoid the possibility that a line of sight is blocked by an intervening optically thick Lyman limit absorber.Proposal # 071 A GALEX View of Galactic F and G Dwarfs
We propose to investigate the properties of Galactic F and G dwarf stars in the GALEX imaging passbands. Our objective is to determine the dependence of the GALEX UV colors and magnitudes of these stars upon basic parameters such as effective temperature, metallicity, age, and chromospheric activity. This is largely an archival program to be based on a dataset obtained by cross correlating GALEX all-sky-survey sources with a number of large F and G dwarf catalogs. From the field star data the dependence of GALEX UV colors and absolute magnitudes, upon effective temperature (via optical colors), metallicity, Li-based ages, and various chromospheric and coronal activity indicators will be derived. In order to test more precisely for sensitivity of UV colors to stellar age, we propose GALEX imaging of the open cluster NGC 2281 (age 0.4 Gyr) for comparison with archival images of M67 (age 4 Gyr). The F and G dwarfs in these two clusters have ages that differ by a factor of 10, thus providing a wide baseline to test for any age dependence of most particularly the FUV fluxes.Proposal # 073 The UV Dependence of the Physical Properties of Quasars
We propose to determine how the physical characteristics of quasars, e.g. black hole mass, accretion rate, luminosity, and line strength, are related to their UV properties. We will use the GALEX GR2 archive cross-matched with the SDSS DR5 quasar catalog to construct a dataset of UV to optical parameters for nearly 30,000 spectroscopically confirmed quasars. From our previous work on over 6300 GR1/SDSS matched quasars (Trammell et al. 2006), we expect a 50% detection rate of SDSS quasars in the GALEX dataset in both the NUV and FUV bands (85% for NUV detections alone). UV data for the vast majority of the cross-matched quasars has been obtained only by GALEX. The large dataset will allow for the unambiguous separation of UV dependencies on up to four parameters. Measurements of the continuum luminosity, black hole mass, and emission line strength parameters from SDSS spectra are being made. Each of these properties is expected to be related to the spectral shape of the UV portion of the SED, shortward of Ly-a emission. We will construct complete UV through optical SEDs of the very large dataset, correlate the UV properties with the measured physical parameters, and directly test theoretical predictions for these relationships.Proposal # 075 Hot Populations in Galactic Globular Clusters
We propose to obtain GALEX UV images of 9 Galactic globular clusters. Recent studies suggest that the helium abundance variation within a cluster is the major parameter controlling the production of EHB stars. HB stars with surface temperatures exceeding ~19,000 K have very thin envelopes, and the energy output from the helium-burning core dominates over that from the hydrogen burning shell. Since helium-rich stars have smaller core mass, they have a lower surface luminosity. Hence, if EHB stars originated from helium-rich subpopulation, their average UV brightness would appear fainter than the zero-age HB level of normal helium abundance. Our goal is to reliably measure fluxes of the EHB stars in Galactic globular cluster to test this helium-rich hypothesis of the production of EHB stars. We are also planning to measure integrated fluxes for all observed clusters, which will serve as templates for studying extragalactic globular clusters in the UV.Proposal # 078 UV Observations of Nearby Star-Forming Galaxies
Understanding the star-formation history of the universe is key to our understanding of the formation and evolution of galaxies. Studying the star-formation of galaxies out to large redshifts is currently the focus of several large-scale programs using multiple NASA facilities, including GALEX. Interpreting the results of such efforts, however, requires a detailed understanding of the nature of star forming galaxies in the local universe. We propose an archival study based on a ground-based sample of H-alpha emission-line galaxies at z < 0.1 combined with existing ground-based optical and near-IR imaging (NOAO) and archival GALEX data centered on the NOAO Deep Wide-field Survey (NDWFS) Bootes field. This field also has archival radio, x-ray (Chandra), and mid and far-IR (Spitzer) observations. Combining the optical (H-alpha, and multiband photometry) data with FUV and NUV photometry from GALEX will allow us to better understand the nature of dust extinction in nearby star forming galaxies and improve estimates of star-formation rates in the high-redshift universe.Proposal # 079 Star Formation Distribution in Field Ellipticals
We propose to use GALEX to study the distribution of recent star formation in a volume limited sample of field elliptical and S0 galaxies. The resolution will be sufficient to separate a potential central starburst from more extended or radially distant concentrations of star formation. Such morphological work can help to determine the merger history of each object, and comparisons of these systems with other samples -- at higher redshifts or in clusters -- will yield important clues about the differences and similarities in the evolutionary tracks of such systems. Follow-up studies with the VLA will then allow valuable determinations of the gas surface densities of these galaxies and thus any applicable HI star formation laws, if such laws exist.Proposal # 081 Deep Grism Survey of the Hyades Cluster
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 limited by faintness of the cluster members and the usual limitation (of slit spectrographs) to observe them one at a time. Here, we propose to image four rich fields in the Hyades with the GALEX grisms to capture C IV (and Mg II 2800) in about 30 cluster members of late spectral type (F-K), mostly main sequence stars. The highly 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 the young Sun relevant to the erosion of primitive planetary atmospheres by coronal ionizing radiations and mass ejections. The spatial multiplex advantage, sensitivity, spectral isolation, and long stare capability of GALEX are ideally suited to the project.Proposal # 082 Identifying the Missing Young Low-Mass Stars with the GALEX Archive
We propose an archival study to combine the GALEX/All-Sky Imaging Survey (AIS) with extensive ground-based photometric and proper-motion catalogs to identify the nearest young low-mass (M-type) stars. While there has been much recent progress in finding nearby solar-type stars in young moving groups (<100 Myr, <100 pc), such work has largely overlooked the much more numerous low mass stars. These "missing" M dwarfs represent an important and thus-far neglected population for understanding circumstellar disk evolution and planet formation. From a pilot study, we have found that GALEX offers unprecedented sensitivity in detecting young, low-mass stars, as their high levels of stellar activity lead to strong UV excesses. We will mine the existing and planned AIS data releases to select candidate nearby (<150 pc) M dwarfs. We will acquire follow-up optical spectroscopy of GALEX selected candidates to confirm their youthfulness, to measure their 3-dimensional space velocities in order to establish kinematic membership with the known young moving groups, and to study stellar activity diagnostics over a wide range of stellar mass. Our proposed mining of the GALEX dataset will greatly extend the census of young stars near Earth, identifying many of the most promising, nearest targets for intensive ground-based and space-based follow-up studies of planets and circumstellar disks. Our objectives are directly related to NASA's goals of detecting and understanding extrasolar planets and their formation.Proposal # 084 Star Formation in Low Mass ALFALFA Galaxies
We propose to obtain moderate integration targeted GALEX observations of a sample of nearby, low mass galaxies detected in the HI line by the newly initiated 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 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 ages and trace the sites of the youngest stellar populations, even in systems where the current/past star formation activity has been very low. The target list has been extracted from the year 1 ALFALFA dataset to include objects that are nearby and low mass and will probe a range of cosmic environments within the Local Supercluster.Proposal # 086 Star Formation and HI Content within the ALFALFA Volume
We propose to conduct a correlative study of the UV flux extracted from archived GALEX imaging data with the corresponding HI detections contained in the Arecibo Legacy Fast ALFA (ALFALFA) survey to derive the bi-variate UV luminosity - HI mass function and to investigate the relationship of the atomic gas content to the UV light in galaxies throughout the range of cosmic densities characteristic of the local volume to z < 0.06. The direct comparison of HI masses and contents of samples selected separately by UV flux, as well as by optical/NIR/radio flux and by HI criteria, will prove critical to the understanding of both selection bias and the astrophysical processes that trigger and regulate star formation within atomic gas disks at the current epoch. GALEX UV fluxes are critical to the determination of the star formation rate and overall stellar age. We will use the UV detections to characterize recent star-formation in the HI-detected galaxies and to locate the sites of the youngest stellar populations within extended HI features. Starting by UV selection, we will examine the GALEX detections in the same volume to determine where star formation is occurring in these fields, and then use the ALFALFA data to characterize the gas properties associated with the star formation especially as a function of local environment.Proposal # 087 Tracing with GALEX the eventful life of field early-type galaxies.
Early-type galaxies (ETGs) are considered fossil evidence of the process of galaxy evolution. Recent optical studies suggest that, on average, field ETGs are younger than their cluster counterparts. This is likely the consequence of accretion/merging episodes that leave their signature in a young stellar population. We can overcome the problem of age-metallicity degeneracy, which severely limits our understanding of ETG evolution, by combining UV (GALEX) data with optical and MIR data. The complete UV - to - MIR SED will enable us to quantify the importance of recent rejuvenation events that are likely to be driven by accretion/merging episodes. GALEX NUV and FUV band photometry is crucial to constrain both the mass of gas converted into stars during approximately the last 100 Myr as well as the dust attenuation in the galaxy nucleus. We have applied the method to the interacting S0 galaxy NGC 4435: GALEX data have been crucial and have allowed us to measure a SFR as low as 0.05 M(solar)/year involving 1.5% of the total galaxy mass. Given GALEX's sensitivity to very low SFRs we propose imaging of 16 selected field ETGs for which our team has optical spectra and has been awarded Spitzer-IRS observations. The proposed observations will be modeled to derive the SFR and age of the younger population in a well-studied sample of field ETGs. Comparison of the results to similar studies of ETGs in clusters will shed light on environmental effects on the evolution of these galaxies. Our comprehensive study of a nearby sample will be indispensable for the interpretation of distant ETGs.Proposal # 089 UV Imaging of a Representative Sample of Nearby Blue Compact Dwarf Galaxies
Blue Compact Dwarf galaxies (BCDs) are extreme examples of star-forming dwarf galaxies. They exhibit the highest specific star-formation rates (star-formation rates per unit mass) of any class of galaxy in the local universe. Despite decades of study, many important questions remain unanswered regarding these enigmatic stellar systems. We propose to obtain NUV and FUV imaging data for a large, representative sample of 22 nearby BCDs (16 through new observations, 6 from the GALEX archives). When combined with our extensive set of optical, NIR, and radio data, these UV images will allow us to address a number of key questions regarding the details of the star-formation events in these systems. Among the issues we plan to address with these data are whether we can detect evidence for a metallicity dependence to the standard star-formation rate conversion factor. In addition, we hope to be able to use the UV data to help constrain, for the first time, the range of ages for the star-formation events in BCDs.Proposal # 091 Stellar Magnetic Activity on Young (8-200 Myr) Local Association Dwarf Stars
Young (10-200 Myr old) stars have very high levels of stellar activity (e.g. UV and X-ray emission) that can strongly influence the formation and evolution of their protoplanetary systems. The high energy emission, both as radiation and particles, resulting from magnetic activity on the central star controls the thermal structure of disks, the formation process of planetesimals, and the photoexcitation and photoionization of protoplanets and young planetary atmospheres. We propose a GALEX archival investigation of the FUV emission, which is dominated by transition region [TR] (100,000 K) emission lines such as C IV, from a sample of over 40 Local Association dwarf stars with ages between 8 and 200 Myr to measure and characterize the EUV/FUV radiation field impacting their protoplanetary systems. We shall develop methods to measure continuum-corrected TR emission fluxes from GALEX FUV and NUV band photometry.Proposal # 093 GALEX Observations of Comet 8P/Tuttle
Comets are primordial objects left over from the formation of the Solar System. Their study is therefore directly relevant to NASA strategic Sub-goal 3C: "Advance scientific knowledge of the origin and history of the solar system...." Comet 8P/Tuttle is a short-period Halley-family comet well positioned for GALEX study as it approaches its next perihelion, 2008 January 26. GALEX has successfully observed two Jupiter family short period comets (9P/Tempel 1 and 73P/Schwassmann- Wachmann 3) and one long-period comet (C/2004 Q2 Machholz). GALEX is sensitive to several cometary emission lines, the brightest of which include C I 1561 A and 1657 A, CS 2576 A, and OH 3080 A. Operated in grism mode, with its 1.2 degree diameter FOV, GALEX can simultaneously provide high-quality surface brightness and radial profile information. In the case of the C I lines, radial profiles provide critical information on the lifetimes of parent carbon-containing molecules. One of these molecules, CS, will be simultaneously studied, providing insight into its own enigmatic production rate variation vs. heliocentric distance as 8P/Tuttle moves from 1.5 AU to 1 AU. The brightest emission, OH 3080 A, is a well-known proxy for water, the primary constituent of comets. As very few wide-field studies of OH have been done in low production rate comets, GALEX observations of OH in 8P/Tuttle will provide an important benchmark for past and future observations.Proposal # 095 GALEX Survey of the Atacama Cosmology Telescope Strip
We propose imaging of the Atacama Cosmology Telescope (ACT) strip with GALEX. In conjunction with the ACT collaboration optical follow up program, GALEX observations will enable us to achieve accurate photometric redshifts for galaxies lensed by the ACT clusters in the redshift range 0.6 < z < 1.2. In addition to the mm observations provided by ACT, we have obtained optical (griz) observations from the Blanco Cosmology Survey. The ACT collaboration will construct a weak lensing map of field galaxies by clusters in the ACT strip. Accurate photometric redshifts of the lensed field galaxies are needed in order to obtain accurate (to within 10%) mass estimates for the dark matter of clusters. Most galaxies lensed by clusters at z > 0.5 are blue and therefore their photometric redshifts are difficult to measure with bands that only sample the 4000 °A break. By obtaining GALEX photometry we will be able to sample the Lyman−_ break as well, a feature which is more pronounced in blue galaxies. We will thus be able to increase the accuracy in the photometric redshift to 0.06 rms. One of the main goals of ACT is to measure the equation of state of dark energy with high accuracy (a few %) by obtaining masses for ACT clusters through weak lensing; this accuracy will not be possible without the proposed GALEX observations. Additionally, a welcome by-product of these observations will be a measurement of star formation in the galaxies in ACT clusters for z < 0.5. The ACT strip is unique in the sense that it will contain optical and mm observations of clusters selected by the Sunyaev-Zeldovich effect, i.e. a mass selection. The addition of GALEX observations to the ACT strip will provide a Legacy set of observations for the astronomical community.Proposal # 103 Measuring Star Formation Rates in Clusters of Galaxies with GALEX
Recent UV and optical observations have revealed that a fairly high percentage of clusters of galaxies with short cooling times in the X-ray emitting gas (cooling flow clusters) show evidence for large amounts of star formation, but that there is little evidence for star formation in noncooling flow clusters. Thus the origin of this star formation is likely to be related to the presence of short cooling times in the X-ray gas. We have obtained XMM Optical Monitor UV imaging data in one color band for 15 clusters and find that the ratio of UV light to inferred X-ray cooling rate shows a range of ~100, with some clusters having an implied star formation rate consistent with the X-ray cooling rate and others showing no evidence for 'excess' UV light. We propose to use GALEX data to: 1) confirm the presence of 'excess' UV light in cluster centers which is not related to the old stellar population; 2) use GALEX FUV and NUV colors to age date this population; and 3) use the higher signal to noise GALEX data to derive a surface brightness distribution for the UV light and directly compare it to the optical light and the X-ray inferred cooling flow profile.Proposal # 104 Metal Abundances in Select Low-Redshift Damped Lyman-Alpha Systems
QSO absorption-line observations are a means to survey and study galaxies based on gas cross-section selection. Studies of QSO damped Lyman-alpha (DLA) systems are particularly important. They track the neutral gas component of the universe and hence provide the means to measure the evolution of the cosmic neutral gas phase metallicity. However, due to the need for UV spectra, metallicity studies of DLAs are scarce in the redshift regime (z<1.65) that corresponds to the last 10 Byrs in the history of the Universe. He we propose to obtain GALEX UV spectra of carefully selected lowredshift (z=[0.8,1.2]) absorption systems in order to measure their HI column densities. From thousands of systems identified in SDSS DR4, we have chosen ones for observation that will permit us to determine the frequency of near solar metallicity systems. The fact that DLA element abundances are usually well below solar is a major outstanding problem in the interpretation of DLA metallicities. While the GALEX spectra have low resolution, we show that they are more than adequate to measure HI column densities in the DLA regime. The results can then be used to derive abundances for several important elements (e.g., Cr, Fe, Mn, Si, Zn). This program will significantly increase the number of available low-redshift measurements and improve both the empirical constraints on and interpretation of cosmic metallicity in an important redshift interval.Proposal # 105 Mean Extinction from QSO Absorption-Line Systems at z=[0.4 0.9]
Studies of the spectral energy distributions (SEDs) of samples of quasars with and without intervening quasar absorption-line systems can be used to measure dust extinction in the Universe. Observations indicate that the dust resides in regions which contain large amounts of neutral hydrogen gas, and we have developed a method to identify such regions. We have analyzed more than 40,000 quasar sightlines and found approximately 14,000 MgII absorption-line systems which can be used to trace this neutral gas. Approximately 5,000 of these absorbers lie at absorption redshfts z<0.92, where internal Lyman limit absorption in at least one of the two GALEX UV imaging bands will not be a problem. Only attenuation due to dust at the absorption redshift will be present. About 40% of our quasars with z<0.92 are in the GALEX archives. We will use the detections to construct UV to near-IR composite SEDs of quasars with and without absorption. Our analysis, applied to different subsamples, will provide cosmological measurements of the amount and distribution of dust at z=[0.4,0.9].Proposal # 107 Grism Observations of OB Stars in M31
We propose GALEX/grism spectroscopy of the OB stars and associations in M31 that the spectacular GALEX mosaic (Thilker et al. 2005) has revealed. Spectral classes will be determined based upon the strength and appearance of C IV 1550 A, the Si IV doublet at 1400 A, and other weaker features of C III, Si II, and Fe III between 1400-1600 A. OB associations will be identified from the listings in van den Bergh (1964) and Magnier et al. (1993). A technique of population synthesis that employs a combination of observed and computed spectra will be employed to determine the stellar composition of the associations. Peculiar stars or associations that display C IV emission will be identified. The Si and Fe abundances will be estimated from the spectra of apparently individual or dominant cluster stars, and we will look for evidence of a metallicity gradient in the galaxy. The project will yield abundances from a young stellar population to compare with those determined from ground-based photometry of OB cluster stars and globular clusters, the spectra of A supergiants, and planetary nebulae. M31 will be covered with two grism observations of selected GALEX NGS fields.Proposal # 108 Populating the Observational HRD of White Dwarfs with GALEX
GALEX's UV filters provide a uniquely powerful tool for selecting and characterizing hot stellar objects compared to purely optical photometry, which is relatively insensitive to hot stellar temperatures. We have compiled a list of White Dwarf candidates selected from GALEX 2-band UV photometric data for which 5-band SDSS optical photometry is also available. A cross-correlation search with SDSS's DR5 release showed roughly 2000 of these candidate objects have SDSS optical spectra. A subset of these also have GALEX UV spectra. We propose to combine and analyze the archival spectra to (a) verify the WD classification of the candidates derived from the photometric data and (b) determine their stellar parameters (e.g., gravities and effective temperatures) by comparing the spectra with large grids of non-LTE stellar atmosphere models which we have already computed. This work will produce a statistically significant sample of WDs which will be used to populate the observational HRD of these hot evolved objects for the first time. A significant fraction of these candidates appear to have a main sequence companion; in such cases the spectral fit and parameters of the system will also give a ``spectroscopic'' distance, more accurate than can be inferred from kinematic-based methods or photometry.Proposal # 110 The Ionization State of ULIRG Winds
GALEX observations have largely ignored Ultraluminous Infrared Galaxies (ULIRGs). Ultraviolet light emerges from these dusty starbursts along only the least obscured sightlines, as shown by the Goldader et al. HST observations. We request new UV photometry of 37 ULIRGs, to be supplemented by 4 datasets in the GALEX archive, to measure the ionization state of sodium in their galactic winds. Empirical constraints on wind velocities, mass loss rates, and solid angle are critical for identifying the physical mechanism driving these winds. The optical resonance doublet NaI 5890,96 has been employed to measure outflow velocities and column densities for many ULIRGs. However, the ionization correction for sodium likely varies by over an order of magnitude among objects, leaving the mass loss rates highly uncertain. Murray et al have recently demonstrated that the strength and spectral index of the UV continuum provide definitive constraints on the ionization state of sodium in these outflows. The proposed program would constrain variations in the ionization fraction of sodium among ULIG outflows, thereby vastly improving estimates of mass loss rates. This work will generate an important legacy of GALEX observations of nearby, dusty starbursts.Proposal # 117 The Effect of Substructure on the Star Formation Histories of Cluster Galaxies
We propose to expand our multiwavelength survey of intermediate redshift galaxy clusters to include new GALEX observations of two additional clusters, Cl0939+4713 (z=0.41) and MS0016+16 (z=0.55), which are characterized by an inhomogeneous galaxy distribution. Combined with our results on two previously studied clusters, we will test the hypothesis that the dominant physical mechanisms working to quench star formation within clusters depend not only on local environment, as we have shown, but also on the overall large scale structure. GALEX provides a unique and sensitive measure of unobscured star formation that changes on short timescales (10 Myrs). The combination of GALEX imaging with the extensive multiwavelength data available on these clusters will allow us to trace the star formation histories of cluster galaxies across a wide range in cluster environment, and allow us to evaluate the importance of cluster substructure in the transformation of infalling galaxies.Proposal # 121 Using GALEX to Discover the Origin of the Black Hole-Bulge Mass Relation
Both observations and simulations suggest that galaxy-galaxy mergers can transform star forming, disk-dominated, gas-rich galaxies into early types. Two critical questions that remain unanswered are 1) what fraction of early types evolved from such mergers and 2) whether mergers can explain the startling connection between a galaxy's small- and large-scale physics implied by the empirical black hole-bulge mass relation. Combining UV photometry with optical spectra has the potential to answer both questions by drastically improving the constraints on when the star formation ended in a galaxy undergoing a late-to-early type transition. Here we propose to obtain UV photometry for a unique sample of 18 post-merger, post-starburst, late-to-early type transitional galaxies. With these data, we will determine the fraction of modern-day early types that might once have been post-merger, post-starburst galaxies by comparing the duration of this phase with the known number of galaxies passing through it. The narrow age constraints arising from the UV fluxes are also an exciting new test for popular theories in which nuclear feedback during mergers quickly extinguishes both star formation in the bulge and any subsequent black hole growth, leading to the black hole-bulge mass relation. This test is possible only because the UV data are particularly sensitive to stellar ages of less than a few 100
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