GALEX Guest Investigator Cycle 1 Abstracts Header Body-ED
Galaxy Evolution Explorer

This website is kept for archival purposes only and is no longer updated.

Site Home Page





Instrument & Calibration



Cycle 6 Information

GALEX Project at Caltech

View an Abstract from CYCLE 1

Click on the proposal number for the abstract you would like to view.

004, 005, 008, 009, 013, 014, 022, 023, 024, 025, 026, 031, 032, 033, 035, 036, 037, 038, 039, 040, 041, 043, 044, 045, 047, 052, 055, 056, 057, 059, 060, 061, 063, 065, 067, 071, 073, 074, 075, 077, 078, 079, 080, 081, 085, 089, 091, 092, 093, 094, 095, 096, 097, 098, 099, 100, 102, 104, 108, 109, 110, 113, 114, 115, 117

Proposal 4: Snapshot imaging of NFPS galaxy clusters

We request snapshot imaging for a sample of 28 nearby X-ray selected galaxy clusters from the NOAO Fundamental Plane Survey (NFPS), to investigate the stellar populations of early-type galaxies in the cluster environment. The data will be used to complement existing optical mosaic imaging data, from which broadband colours and morphologies are already in hand. Optical spectroscopy has been obtained for ~1200 red-sequence galaxies in these clusters, yielding redshifts, velocity dispersions, and absorption line strengths. The proposed GALEX observations will be used to test the consistency of optical versus NUV constraints on ages and metallicities. Additionally, the rich NFPS database will be used to search for correlations of the FUV-upturn with optical galaxy properties and with the cluster environment. We will image to a depth sufficient for ~15 sigma (NUV) and ~7.5 sigma (FUV) detection of elliptical galaxies to the limit of the NFPS spectroscopic sample, at R_tot=17. The depth requirement is limited by the need for accurate FUV fluxes to correct NUV-optical colours for the effects of the UV-upturn population. Although AIS data are sufficient to detect the objects of interest, they are much too shallow to yield the accurate fluxes required for this programme. Our proposed observations complement deeper PI observations of low-z clusters (which target only four clusters with greater depth).

Proposal 5: Diffuse UV Background

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.

Proposal 8: Serendipitous source search

We shall implement newly developed software tools to search the GALEX archival all-sky survey data for both transient and variable UV sources. Our aim is to detect and model the UV emission from stellar flares, dwarf novae, soft X-ray transients and intrinsically variable stars such as RR Lyraes and Cepheids. Preliminary inspection of 37 observations of 1 of the 80 proposed Deep Imaging Survey fields has revealed a Mv = 13.5 RR Lyrae stars that exhibits over 5 magnitudes of variability in the far UV. Such large amplitude UV variations provide a more stringent limit to the stellar metallicity and/or temperature as derived from stellar atmosphere models for this class of star. We also hope to detect the associated UV emission from known gamma-ray bursters, which if detected would help constrain their luminosity function. Most of these serendipitous detections will require follow-up ground-based observations to determine their optical identification.

Proposal 9: SUNGG

Much of our understanding of star formation in local galaxies is based on H-alpha imaging which shows that O stars are concentrated into compact HII regions, and that there typically is a sharp truncation radius to star formation. Ultraviolet (UV) imaging of galaxies reveal a different picture - there is less contrast between HII regions and the field, and the truncation radius is not as apparent. This striking difference has potentially strong implications. The extensive and diffuse UV light may trace field star formation that (1) perhaps has a non-standard and varying Initial Mass Function (IMF), (2) may be an in situ ionization source for the Diffuse Ionized Gas, and (3) could serve as a source population for isolated supernovae, potentially providing the energy to stabilize extended HI disks. The implications are so profound that they call for a thorough re-examination of the star formation law and the IMF. This Survey of Ultraviolet emission in Neutral Gas Galaxies will meet the need by providing the crucial deep UV images that trace the distribution of stars most responsible for heating and structuring the interstellar medium, using a comprehensive sample covering all types of galaxies with an ISM, and thus capable of forming stars.

Proposal 13: UV Properties of Luminous Infrared Galaxies

We propose to study all ultraluminous and luminous IR galaxies (LIRGs) with L_ir > 10^{11.6} L_sun in the IRAS Revised Bright Galaxy Sample that are accessible by GALEX. Although they are rare in the local Universe, recent IR and sub-mm surveys indicate that LIRGs dominate the radiant energy density of the Universe at high redshifts. In order to interpret rest-frame UV observations of high-redshift IR/sub-mm galaxies, it is essential to measure UV properties that can be observed with high spatial resolution and high S/N only in their nearby analogs. These proposed GALEX observations are therefore of critical importance for understanding the origin and evolution of luminous starburst galaxies and AGNs in the local Universe and through cosmic time. We request deep integrations of 3 ksec (2 orbits) for each of 33 objects, which will be combined with an archival study of 16 LIRGs and ULIRGs contained in the GALEX Nearby Galaxy Survey. Primary questions to be answered include: How do the star formation rates derived from UV emission vary with the stage of the interaction/merger, the mass ratio of the galaxies, the geometry of the encounter, and the properties of each galaxy as known from multiwavelength observations? How do the proportions of UV emission contained in the nuclei, spiral arms, tidal tails, and disk overlap regions change as a function of the interaction/merger stage? When do star-forming regions in tidal tails first light up, peak, and fade? IR data for many objects in our sample are available from IRAS and ISO, and more will soon appear in the public SST archive. We will analyze these data with the GALEX images to address these additional questions$\colon$ What are the proportions of star formation in UV-bright regions with low extinction vs. dust-enshrouded regions? How do UV extinction maps (from UV/IR images) depend on the properties of each system? How do the emergent UV fluxes compare to predictions from models of the UV interstellar radiation field strengths derived from far-IR line ratio diagnostics? What fraction of UV radiation is escaping from LIRGs and ULIRGs into the intergalactic medium?

Proposal 14: UV imaging of NGC2442

NGC 2442 is a well-studied, southern, peculiar barred spiral galaxy for which modelling has suggested an interaction with a nearby companion. This galaxy is important for studying the relationship between disk-wide starburst activity, nuclear activity (in the form of both a starburst ring and a LINER AGN) and the interaction which may have triggered these phenomena. NGC 2442 has been observed by {\em Spitzer} as a commissioning target with the IRAC and MIPS instruments. By taking UV data with {\em GALEX} we hope to learn more about the starburst-AGN connection, the extinction towards the regions of intense star formation in both the disk and the nucleus, and the excitation of the PAH emission. These results can be applied to studies of galaxies at higher redshift, where only integrated SEDs are available.

Proposal 22: A wide field UV study of two z~0.5 clusters

Clusters of galaxies are excellent laboratories in which to study how different environments influence the star formation and morphologies of galaxies. GALEX imaging will provide crucial UV fluxes for cluster members defined from a comprehensive wide-field survey of the two best-studied z~0.5 clusters, Cl0024+17 and MS0451-03. HST morphologies, multi-color ground based photometry and Keck spectroscopy are already available to the turn-around radius (~ 5 Mpc). This unique multi-wavelength program aims to isolate the physical processes responsible for transforming gas-rich field galaxies as they progress through the cluster potential. UV fluxes will allow us to measure star formation histories on 100-1000 Myr timescales. Together with spectroscopic diagnostics, a detailed picture of star formation activity will be deduced for hundred of galaxies, enabling us to distinguish between short bursts (as expected from ram pressure stripping) and longer duration activity (as expected from harassment). The GALEX data will also provide important measures of the UV continua for the quiescent early-type population at a look-back time of ~5 Gyrs. This signal has been studied locally and is thought to arise from hot post-main sequence stars. However, the relevant physical quantities are poorly understood. The radial dependence of this UV excess at z~0.5 will provide additional insight into the environmental history of the early-type population.

Proposal 23: Pilot Search for Binary Companions in Dying Stars

The outstanding problem significantly impeding progress in our understanding of the evolution of low- and intermediate-mass dying stars is that, although this evolution depends on the mass-loss rate, we do not know how the mass-loss depends on extrinsic factors like binarity, as opposed to intrinsic stellar properties such as luminosity, effective temperature, and metallicity. HST imaging has shown that the dynamics and symmetry of mass-loss starts to change dramatically during the late AGB phase, and binarity is widely held to be responsible for this change. However, direct observational evidence of binarity is very difficult to obtain because the primary AGB stars are much more luminous at optical/infrared wavelengths -- it is only in the far-UV that the companions (which are generally likely to be hotter) outshine the former. We therefore propose to use GALEX's NUV imaging capability to make a pilot search for the NUV flux from hot companions in a sample of cool AGB stars. The majority of these stars have been selected from the Hipparcos database with indirect evidence for the presence of nearby (unresolved) companions and a smaller number from catalogs of AGB stars with CO emission signifying substantial mass-loss.

Proposal 24: Comet 9P/Tempel 1 During the Deep Impact Encounter

We propose a series of observations of the periodic comet 9P/Tempel 1 in conjunction with NASA's Deep Impact mission. This mission consists of a spacecraft that will release a 360 kg impactor into the nucleus of the comet on July 4, 2005. Our primary objective is to study the changes in the gaseous coma, particularly as regards the volatile species CO and CO2, resulting from excavation of subsurface material due to the impact. To this end we plan to obtain both far- and near-ultraviolet spectra with GALEX before, during, and following the impact. Changes in cometary activity from the quiescent state will be monitored using emission from the (0,0) band of CS at 2576 A. We may also be able to detect Cu I fluorescence of the residual vapor from the copper impactor.

Proposal 25: Evolution of Stellar Dynamos

The origin of stellar activity in ancient evolved stars remains a mystery. The rotationally induced global dynamo, present during the main-sequence, is expected to have decayed through angular momentum loss in a coronal wind while evolving towards the red giant branch (RGB). Mass loss during the ascent of the RGB further damps any rotation induced dynamo. Yet Population II giants show signatures of continued chromospheric heating and mass loss. The physical mechanisms responsible for both these forms of activity are unknown. We propose sensitive GRISM spectroscopy of a sample of Population II metal-deficient field giants to help establish the relative importance of different chromospheric cooling channels. These spectra will help us understand how the structure of stellar chromospheres respond to large changes in metallicity, and provide clues as to whether the heating mechanisms are magneto- or hydro- dynamic in origin. These observations will be an important addition to the archive of Population II UV spectra.

Proposal 26: Star Formation in Colliding Galaxies before Merger

We propose to use GALEX to study stellar populations and star formation morphology in a well-defined sample of nearby colliding galaxies with a wide range of tidal and `splash' structures. Galaxy interactions were likely far more common in the early Universe than in the present, thus our study will provide a nearby well-resolved comparison sample for high redshift studies. We will combine GALEX NUV and FUV images with data from other wavebands and with stellar population models, to create extinction maps and to determine the history of star formation as a function of position in the galaxies. These results will be compared with dynamical models of the interactions, to investigate star formation triggering mechanisms. Our observations will complement those of the guaranteed time Nearby Galaxy Survey project.

Proposal 31: Star formation in HI debris

We propose to use GALEX observations to search for evidence of star formation in the intergalatic HI clouds of nearby galaxy systems. The method, identifying starburst sources (the so called intergalactic HII regions) coincident with HI clouds, has been recently used to demonstrate significant star formation outside of galaxies in Stephan's quintet. Mendes de Oliveira et al. 2004, (see also found several candidates of such star-forming regions using multi-slit spectroscopy which were confirmed by the GALEX pre-release observations of this spectacular interacting group. For this proposal we chose eight nearby systems (z < 3200 km/s), most of which are interacting or merging, which contain intergalactic HI clouds. They were selected from the HI Rogues Gallery of HI maps of galaxies and groups ( Our main goal is to measure or set limits on the UV flux for the intergalactic HII regions that may be present in intergalactic HI clouds, in order to determine their ages and masses. Finding widespread, young, star-forming regions in the eight HI intergalactic clouds, indicating `in situ' formation of these objects, will be strong evidence that this is an efficient mechanism for producing and mixing metals in the intergalactic medium. This may have been even more important in the early universe, when galaxy-galaxy interactions were more frequent and tidal debris more common.

Proposal 32: Star Formation in the Intergalactic Medium

Recent observations have shown that star formation may occur in the intergalactic medium outside any pre-existing stellar structure. Many of such giant HII complexes are progenitors of super star clusters or -- if they are very luminous -- dwarf galaxies, and are associated with tidal debris found in the vicinity of interacting systems. How star formation proceeds in this particular, though simple environment, is so far unknown. We propose to image with GALEX two interacting systems showing tidal tails solely made of ejected gaseous material, in which we have already detected the formation of star-forming tidal dwarf galaxies. Both systems (NGC 5291 and NGC 4694/VCC 2062) lie in the outskirts of clusters of galaxies. Their UV fluxes will complement our multi-wavelength data set on these objects; they will be used to (1) study the recent star formation history and in particular infer the onset of the starburst actvity in the tidal tails (2) determine the UV SFR which we will compare with that derived in the optical and infrared, thus giving hints on the extinction law (3) estimate the star formation efficiency and compare it with that measured in grand design spirals and in classical dwarf galaxies.

Proposal 33: observations of edge-on spiral galaxies

We propose to observe spectroscopically a sample of 10 nearby edge-on spiral galaxies in order to take advantage of their projected area to create a natural slit. We select galaxies with a major axis larger or equal to $\sim$ 5' in order to have a good sampling of the radial variations. The minor axis must be small enough to obtain spectra with a moderate spectral resolution. The galaxies are also selected to cover the widest possible range of characteristics (morphological type, amount of extinction) and to have a lot of complementary data available. We will have $\sim$10 spectra of moderate spectral resolution and high signal to noise ratio along the major axis of the galaxies: \The analysis of this sample will provide crucial diagnostics of the stellar content, history, and dust extinction inside disk galaxies, and their radial variations. We will: (1) derive dust/star geometries, and search for systematic trends; (2) derive attenuation curves, and determine the presence/absence of the 2200 A dust feature; (3) determine the statistical mix of young and old populations in the dust-corrected disks, and derive star formation histories. These data will provide baseline templates of the UV spectral distribution of spiral galaxies, for the interpretation of the GALEX photometric data, and for studies of low- and intermediate- redshift galaxies.

Proposal 35: Galaxies and quasars in the largest structures

Rare, large-scale structures (LSS) are predicted by LambdaCDM models, providing essential size/contrast/evolution observational tests. While galaxy surveys (SDSS, 2dF) revealed structures on ~100 Mpc scales at z~<0.3, at z>~1 areal coverage is insufficient to reveal the complete extent of structures via galaxies. How large and massive are the largest structures at z~1? Quasars provide z~1 structure-tracing proxies, though their unclear relative bias to galaxies/clusters hampers z~>1 LSS mass estimates. At z~<0.3, quasars prefer high star formation rate (SFR) regions and cluster outskirts; such behavior persists to z~1, near the peak SFR, during ''downsizing'' of high SFR galaxy masses. We propose to probe a 50x100 (65x130)/h2 comoving Mpc region toward two sheet-like structures of galaxies containing clusters at z~0.8 (1.2), as traced by 12 quasars within ~240/h Mpc-wide large quasar groups (LQGs). This unique site within the largest z>1 LSS is an unprecedented chance to investigate the quasar-galaxy-cluster-SFR relation. Only GALEX can provide accurate photometric redshifts for star-forming galaxies in the structures. This field provides the most efficient way to detect simultaneously clusters, filaments and high SFR associated with quasars at z~1, and hence to constrain both hierarchical formation theory and galaxy-quasar-cluster-SFR relations.

Proposal 36: GALEX Observations of Nearby Dwarf Galaxies

We propose to obtain GALEX SNAPs to get deep surface photometry/images in the FUV and NUV for 42 nearby late-type/irregular and some peculiar/merging galaxies. These nearby low-luminosity galaxies are critical to study in the UV, since at high redshifts these were the likely building blocks of the giant galaxies that we see today. The HST UltraDeep Field has shown that their LF was steep enough that these ``dwarf'' galaxies likely completed the reionization epoch at z=6. The FUV escape fraction is currently a major uncertainty in determining whether dwarf galaxies indeed were able to complete reionization at z=6. We do not know how much FUV radiation escapes from nearby dwarf galaxies, likely from holes poked in their interstellar medium+dust through energy deposition by massive stars. By placing strong constraints on their youngest stellar population and dust, GALEX images will allow us to determine the 155 nm escape fraction in nearby dwarf galaxies, and in combination with higher resolution HST/ground-based/Spitzer images, study their hot UV stellar population in detail (at <500 pc resolution). We imaged these nearby objects at high resolution with HST/WFPC2 in the NUV (293 nm) and red (785 nm), plus some with NICMOS at 1.6 micron. We also have ground-based CCD-images in UBVR, plus some SCUBA 850 micron images, while Spitzer 3.5-8.0 micron images are available for some objects and proposed for the remainder. Hence, we can study the precise locations of their stellar populations and dust from the combined data set. The critical part missing in these studies are GALEX 155 and 230 nm images and fluxes.

Proposal 37: Galaxy groups at z=0.4

The galaxy group environment at intermediate redshift (0.3"<"z<0.55) has a critical influence on the evolution of galaxies. However, these systems are poorly studied and understood, especially at UV wavelengths. One reason for this is the difficulty in identifying such low-density systems in an unbiased way. With the recently completed CNOC2 redshift survey, we have compiled the first complete, unbiased sample of groups at this redshift. We also have follow-up high-resolution imaging from the Hubble Space Telescope, and deeper, more complete spectroscopy from the Magellan 6.5-m telescope, and therefore the best available data to study this important environment. We propose to combine NUV GALEX observations of these groups with our existing ground-based UBVRI photometry and spectroscopy to measure dust-corrected star formation rates of galaxies in 19 groups with 0.3"<"z<0.55. In addition, our GALEX fields will include most of the galaxies in the original CNOC2 redshift survey, allowing us to measure the UV luminosity function over the same redshift range, from an unprecedented sample of ~3200 galaxies. By directly comparing our data with galaxies at low redshift (from the Medium Imaging Survey overlap with the 2dFGRS and SDSS) we will determine how the growth of structure in the Universe influences galaxy evolution.

Proposal 38: K-corrections for GALEX

We propose to use archival GALEX observations to characterize galaxy spectral energy distributions in the ultraviolet. Our goal is to create a public tool for calculating K-corrections (that is, the transformations between observed fluxes and rest frame fluxes for redshifted sources). This tool will build on and be compatible with widely-used ones we have already made public for the analysis of optical and near-infrared observations in the Sloan Digital Sky Survey and the Two-micron All Sky Survey. A consistent treatment of ultraviolet, optical, and near-infrared observations will simplify data analysis and improve comparison of low-redshift observations of galaxies (typically optical or near-infrared) to high-redshift observations (often in the rest-frame ultraviolet).

Proposal 39: The outskirts of the Coma cluster

Evolved Coma-like clusters of galaxies are constituted of relaxed cores composed of ''old'' early-type galaxies, embedded in large-scale structures, mostly constituted of unevolved (late-type) systems. According to the hierarchical theory of cluster formation the central regions are being fed with unevolved, low-mass systems infalling from the surroundings that are gradually transformed into elliptical/S0 galaxies by tidal galaxy-galaxy and galaxy-cluster interactions, taking place at some boundary distance. The Coma cluster, the most studied of all local clusters, provides us with the ideal test-bed for such an evolutionary study because of the completeness of the photometric and kinematic information already at hands. The field of view of the planned GALEX observations is not big enough to include the boundary interface where most transformations processes are expected to take place, including the truncation of the current star formation. We propose to complete the outskirt of Coma with an additional corona of 11 GALEX imaging fields of 1500 sec exposure each, matching the deepness (UV_{AB}=23.5 mag) of the fields observed in guarantee time. Given the priority of the target, we also propose one optional Central pointing that includes one bright star marginally exceeding the detector brightness limit.

Proposal 40: Hot White Dwarf Stars in the GALEX Survey

Several bright FUV sources in the GALEX early data release are identified with suspected or known white dwarfs from previous ground-based UV-excess/blue surveys. The full release of the GALEX survey will uncover thousands of new white dwarfs and we propose to identify these objects by correlating the GALEX source catalog with the 2dF Survey of the Galactic caps/poles and with the Sloan survey. Brightest candidates will be immediately followed up at the Apache Point Observatory 3.5m telescope. The new white dwarf catalog will be used to revise the temperature scale of hot white dwarf stars, their luminosity function, as well as their distribution in the Galactic disk.

Proposal 41: Heating Effects

The cataclysmic variables containing magnetic white dwarfs (Polars) can undergo long periods of very low accretion rates, when the accretion column contributes very little light, thus allowing study of the underlying stars. In two of these objects, EF Eri and SDSSJ1553+55, optical and X-ray studies indicate that there is still a heated region on the white dwarf, even though there is no evidence of X-rays from the accretion area nor line emission from a mass transfer stream. We propose time-resolved UV imaging with the NUV and FUV filters on GALEX to resolve the amount of heating occurring during long low state intervals. The results impact the long term evolution scenarios and ages of accreting white dwarfs.

Proposal 43: Coordinated Multiwavelength Observations of AE Aqr

We propose to obtain UV photometry during an ambitious campaign of coordinated multiwavelength (radio, mm, mid-IR, optical, UV, X-ray, and high-energy gamma-ray) observations of the former supersoft X-ray binary and current magnetic propeller AE Aqr. This campaign is built around a Chandra HETG (78 ks) / HST STIS (6 orbits) / VLA (12 hr) proposal submitted for Chandra Cycle 6 observations. Because the requested HST observation covers only the FUV bandpass, samples only one binary orbit, and is affected by Earth occultations, we propose to supplement the HST coverage with GALEX photometric observations for the entire Chandra observation (13 GALEX orbits). The resulting data will measure in two UV bandpasses the phase, amplitude (~40%), and shape of the UV pulsations and the temporal correlation between the UV and X-ray pulsations, thereby elucidating the relationship between these two emission regions.

Proposal 44: A UV spectroscopic survey of nearby supernovae

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 observed by HST in the optical, or by JWST in the near-IR, 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. We propose to rectify this situation using target-of-opportunity GALEX spectroscopic observations of nearby, bright SNe.

Proposal 45: UV Observations of Collisional Ring Galaxies

We propose to image 12 of the largest known collisional ring galaxies with GALEX to directly measure the escaping UV radiation from bright blue outer rings and fainter interior regions. The observations will allow us to 1) compare the direct UV measures of the ring star formation rates (SFR) with SFR derived from our extensive multi-wavelength (optical, IR, radio) data on many of the same systems, 2) explore secondary star formation interior to the brighter outer rings predicted by models to occur in spokes, filaments and inner rings and c) search for UV counterparts to {\it non-stellar}~(i.e. accretion-driven) sources in the outer rings, by analogy with the recently discovery of a dozen extremely luminous X-rays sources found in the Cartwheel ring, and numerous sources in Arp 284. UV observations should be capable of separating intermediate-mass black-hole candidates from more traditional O/B associations by virtue of their expected high UV luminosities. Although relatively rare locally, ring galaxies are more common at high redshift, and their study may represent one of the few ways of probing the physical condition in the outer regions of high-z disks.

Proposal 47: Demographics of Nearby Star-Forming Galaxies

We propose to obtain deep FUV and NUV images for a complete distance-limited (11 Mpc) sample of nearby galaxies for which we have deep \halpha\ and $R$ images. We will use the combined UV and \halpha\ data to quantify the characteristic strengths and durations of starbursts in dwarf galaxies (M$_B \ge -17$), measure the fraction of stars in these galaxies that form in bursts, and study the spatial propagation of the star formation in these systems. The combination of UV and \halpha\ images will yield powerful constraints on systematic errors in the respective star formation rates and histories, and a ``training set'' for cosmological lookback studies which covers the full range of galaxy masses and star formation rates found locally. The project will provide a unique set of deep,spatially-resolved ultraviolet observations of dwarf galaxies, which currently are under-represented in the GALEX observing program. When our proposed observations of 123 galaxies (in 112 fields) are combined with planned GALEX PI team observations of 105 other galaxies in this volume (mostly more luminous spirals), the combined dataset will be a well-defined and fully representative sample of spiral and irregular galaxies within 11 Mpc (and observable by GALEX), a true Legacy for the GALEX mission. In support of this Legacy project we will create a web-based public archive including the processed UV, \halpha, and broadband images and a flux catalog.

Proposal 52: Extremely Isolated Early-Type Galaxies

We propose to obtain GALEX FUV and NUV imaging for four extremely isolated early-type galaxies to contrain their stellar populations and ages. The sample was constructed using stringent morphological and isolation criteria, insuring that these systems exist in very low density environments. From analysis of ground-based optical imaging and spectra (Marcum et al 2004), we have identified four systems which do not appear to be recent (<2Gyr) galaxy group mergers. We wish to test the hypothesis that these systems are either intermediate-aged ''fossil groups'' or passively-evolving, primordial spheroidal galaxies formed in isolation early in cosmic time. Strong support for the latter scenario would be an old (>10 Gyr) stellar population. The UV images requested here are critical for discriminating between intermediate-aged and old populations, a distinction that is crucial to understanding the evolutionary paths of these systems. The proposed observations, in combination with existing groundbased optical broadband data, will provide a benchmark against which the structural properties and star formation histories of elliptical galaxies in more dense environments can be compared.

Proposal 55: CV Search in Open Clusters

Simulations of stellar and dynamical evolution predict significant numbers of CVs to inhabit galactic (open) clusters, along with other unusual blue objects such as extreme horizontal branch stars and white dwarf pulsators; yet known representatives of these populations are sparce due to their faintness in the optical. We therefore propose to use the unique angular and wavelength capabilities of GALEX to image a number of open clusters, in order to recover these objects. Our major objective is to find the predicted - but still missing - population of CVs in these clusters, or to otherwise place strict limits on their occurence. The nature of the very blue and/or UV-variable sources will be determined using follow-up ground-based multiple-object spectroscopy to characterize the various known components (e.g., white dwarfs and white dwarf pulsators, as well as subdwarf OB stars) and any new components of the poorly-understood UV-bright old-disk population. These results will provide significant input for stellar evolution models and for the formation environment of close interacting binary stars.

Proposal 56: UV Properties of Galactic Globular Clusters

We propose to collect deep far and near-UV images of 35 Galactic globular clusters (GCs). This 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. For all the targets, horizontal branch (HB) stars will be clearly resolved, so that the data will allow a detailed study of the UV morphologies of their HBs over a wide range of GC properties. While the relatively low spatial resolution prevents studying the cluster cores, the field of view is large enough that statistically representative samples can be constructed based on stars outside the cluster cores. The exposure times are planned to be long to allow construction of UV color-magnitude diagrams that should be deep enough to sample bright blue stragglers (BS) for all sample targets. The number of known post-AGB and supra-HB stars will be enlarged by a factor of two, allowing for a major boost in the statistics of these short-lived, yet UV-relevant stars. The data will serve as a definitive test of current models for the latest stages of the evolution of single low-mass stars. We will study the spatial distribution of BS for a large sample of GCs, in order to check for the existence of bimodal radial distributions, thus imposing a crucial constraint on the scenarios of BS formation. Integrated UV magnitudes and colors will also be produced, and their correlations with global and structural parameters such as mass, concentration, dynamical state, core morphology, luminosity, age, and chemical composition will also be studied. All these data will serve as a fundamental test of stellar populations synthesis models in the UV, and in particular those currently under development by our own group.

Proposal 57: Multiwavelength Properties of IR-selected AGN

We will use Data Release 1 (DR1) of the GALEX All-Sky Imaging Survey (AIS) to measure the ultraviolet continuum properties of a large new sample of ``hidden'' AGNs. We have identified a complete sample of the 4000 brightest Seyfert nuclei and quasars based on their excess emission at 2$\mu$ in 2MASS. Because this sample was not selected by the usual methods (e.g., blue optical colors or soft x-ray emission), it provides a more accurate, less biased, census of the non-stellar power generated in the local Universe. Most of the AGN in this new all-sky sample were previously unknown. Since our sample covers the entire sky at galactic latitudes larger than 20$^o$, roughly a tenth of our AGN will be covered in DR1. They are among the brightest AGNs in the sky (K$_{agn}$ $<$ 13.5), so even if they are heavily absorbed in the UV, nearly all will be detected in both bands of GALEX AIS. We will measure the strength and shape of the Big Blue Bump, which peaks in the UV. For the 2MASS AGNs also detected by ROSAT, we will calculate $\alpha_{ox}$ and determine if they have sytematically bluer GALEX colors. We will determine if the radio-loud AGNs in our 2MASS sample are redder than their radio-quiet counterparts. We will compare X-ray/UV/optical/IR SEDs of the 2MASS AGNs with those of differently selected AGNs. We will determine how much of the total AGN population is missed (as a result of intrinsically red spectra or dust extinction) by optical/UV or X-ray search methods alone. We will also explore whether sufficiently accurate corrections for incompleteness due to dust can be made having only the UV and optical data. Only the GALEX AIS archive has the UV sensitivity and areal coverage to characterize the SEDs of a sizeable sub-sample of this new obscured AGN population.

Proposal 59: Ongoing star formation in shell galaxies

Current views consider shell structures as a debris of recent minor/major merging event though also weak interaction models could produce long lasting shells on host galaxies possessing a stellar thick disc. Recent optical observations suggest an external origin of the matter, as predicted by merging models. At the same time, a set of observations showing a clear association between cold (HI/CO) gas and stars challenges present merging models In this framework we plan to observe a well selected sample of shell galaxies chosen among those with detected HI and/or CO both in the main body of the galaxy and interleaved with shells. The program will fully exploit GALEX capability in detecting low UV flux and its wide field of view to map faint shell (few percent of the total galaxy luminosity in the optical bands) up to the galaxies outskirts. These data will allow us to verify whether the HI/CO gas rich shells host ongoing star formation processes thus giving independent indications: (1) about the present day star formation; (2) if their presence or absence is consistent with the kinematics of the ionised gas, (3) address merging models which fails in reproducing a coupling between stellar and gaseous shells.

Proposal 60: Are many hot subdwarf stars hidden in binaries?

The Palomar-Green (PG) survey of UV-excess objects yielded an abundant harvest of hot subdwarf (sdO/sdB) stars. Based on visual and near IR (2MASS) colors, about one-third of these are binary (composite colors). Many additional candidate PG stars that might also be hot subdwarfs in binaries were rejected from the final PG catalog, because the Ca II K line appears in their spectra; this line was interpreted to mean that the candidates are cool metal-poor stars (sdF) with low UV line-blocking, so they were U-B color-selected for the wrong reason. An alternate explanation is that these objects are additional composite-spectrum binaries consisting of a hot subdwarf and a main sequence (A or F) star. Optical data alone cannot easily distinguish between these possibilities. A recent theory of binary sdB formation channels predicts that many sdB+A/F systems exist undiscovered, and the rejected PG stars are pointed to as a specific example of where they might be found. With a targeted archival study using GALEX imaging data to search for radiation from a hot star, we can learn whether or not these rejected objects from the PG survey are in fact mostly sdB binaries, with consequences for the origin and numbers of hot evolved stars.

Proposal 61: Variability and Deep Probe of Nearby Galaxies

We propose to use GALEX to obtain deep images of several nearby galaxies but do so by also probing the variability of the ultraviolet emission. Variability is rampant in the X-ray band, where a large fraction (30-50%) of a galaxy's point sources are variable (persistently variable or transient), while in the optical, the fraction of light contributed by variables (minus supernovae) is perhaps 10%. GALEX observations will probe the variability across a broad range of scales for six nearby galaxies. These observations will resolve regions of star formation from the spiral arms, permitting correlations of the ultraviolet and X-ray emission along the arms.

Proposal 63: Finding Sirius-Like Systems with GALEX

One of the major stellar legacies of GALEX will doubtlessly be the discovery of a large number of new Sirius-like binary systems in which white dwarfs are hidden by the optical luminosity of K or earlier type main sequence stars. The true frequency of these systems, as a fraction of the white dwarf population, is presently unknown. There exists good evidence that the present sample of Sirius-like binaries, derived from the optical and EUV, greatly under represent the actual numbers of these systems. GALEX will detect these systems as UV excess objects both in imaging and spectroscopic fields. We propose to use the high quality ground-based photometry in the Sloan Digital Sky Survey in conjunction with GALEX DR1 data to systematically search for, verify, and characterize such systems.

Proposal 65: Galaxy Evolution in the Subaru Deep Field

We propose very deep GALEX imaging of the Subaru Deep Field, one of the darkest and best observed half-degree regions in the sky. We will combine this photometry in the two UV bands with our ultradeep broadband BVRIz imaging (which is nearly as deep as in the HDF's) and our narrow-band imaging in three filters. This combination of GALEX and very high S/N optical photometry will provide one of the largest galaxy samples ($\sim$ ten thousand) for which we can determine accurate photometric redshifts, star formation rates, stellar masses and dust extinctions out to redshifts of z=1 to 2. Optical spectra of a few thousand of these galaxies will be taken at Keck and Subaru in April 2004. We will thus have extensive multiwavelength measures of galaxy evolution based on both their ionized gas and stellar continuum emission. The $\sim$ 30 Mpc (projected) diameter of the SDF is large enough to measure the large-scale clustering of various galaxy populations (to infer their typical halo dark matter masses), and to overcome the large cosmic variance found in smaller fields. We will also combine these multiwavelength data with variability information to study the AGN population back to even higher redshifts.

Proposal 67: Star formation efficiency in LSBs

We propose to obtain FUV and NUV imaging of 26 fields with 27 Low Surface Brightness galaxies (LSBs), for which measurements of their gas content are available. Many observations (large gas-to-light ratio, blue colors, low metallicities) lead to the conclusion that LSBs have a `low' star formation efficiency (defined as the Star Formation Rate -SFR- to gas ratio). Models of the chemical and spectro-photometric evolution of disk galaxies with large angular momentum, indeed characterized by lower efficiencies than in classical spirals, are in satisfactory agreement with these observations. However, we lack at the present time direct measurements of the star formation efficiency to strongly constrain the models and understand the nature of star formation in LSBs. GALEX gives us the opportunity to change this situation by estimating the star formation rate from the UV flux. The GALEX observations of LSBs will provide an unique insight on the star formation efficiency in low-density environment. More specifically, they will allow us to derive the star formation efficiency from the UV/HI ratio, study the (global and radial) star formation `law' at low densities, and compute a new set of models for LSBs implementing this law.

Proposal 71: Old and New Star Clusters in M81

We propose to obtain medium-depth near and far UV imaging of the globular cluster system of the nearby luminous spiral M81. Next to M31, M81 is the closest massive, intermediate-type spiral, making it a prime candidate for such stellar population studies. We have already secured HST/ACS imaging of M81 in a single band (I) to unambiguously identify clusters, and also have deep, multi-filter ground-based imaging using MMT/Megacam. The addition of UV photometry to this data set will allow us to simultaneously assess the effect of horizontal branch morphology on cluster age estimates and to distinguish between any intermediate-aged and old cluster populations. The 1.2-degree field of view of GALEX will enable us to cover the entire spatial extent of the galaxy in a single pointing, and when coupled with follow-up spectroscopy, these data will make the globular cluster system of M81 one of the best-studied to date.

Proposal 73: Star Formation in Compact Groups of Galaxies

We propose to obtain NUV and FUV images of a sample of nearby compact groups and their neighborhoods with the GALEX imaging facility. The main goals for this proposal are: (1) explore whether a relationship between the total star formation rates and the evolutionary state of the group holds, and also to explore the existence of interaction induced nuclear starburst activity in compact group galaxies; (2) study the super star clusters content of the systems in our sample and the relationship to the group properties; (3) search for extended star forming regions in the intragroup medium and (4) perform a morphological multiwavelength study of the sample galaxies in order to quantitatively describe the induced star formation activity with morphological criteria. A sample of field galaxies (already available) will be used to investigate the role of the compact group environment on the UV properties of our sample of compact group galaxies.

Proposal 74: FUV Imaging of the NTT Deep Field

We propose to obtain FUV imaging of the NTT Deep Field, to the same depth reached in other fields by the PI Team's Deep Imaging Survey, in order to determine the *cold* dust content of a complete UV-selected sample extending out to z~1. By combining the GALEX image with our unusually wide (169 arcmin^2) and deep (1 sigma ~ 0.5-0.8 mJy) map of the field's 1.2mm dust emission, a stacking analysis will allow us to probe the mean dust SED of a UV-selected population out to a longer wavelength (and a colder dust temperature) than will be possible from GALEX observations of any other field. This local measurement will inform our understanding of dust SEDs in UV-selected populations at higher redshifts and help constrain the contribution that relatively unobscured star-forming systems can make to the cosmic far-IR background and star formation history.

Proposal 75: Where have all the Lyman-alpha blobs gone?

Lyman alpha emission blobs, up to 100 kpc in size and 10^44 ergs/sec in line luminosity, populate cosmic structures at z>2. Their nature and relation to galaxies and active nuclei remain uncertain from existing data, as does their evolution with cosmic time. Cooling flows of pristine material entering galaxies for the first time, photoionization by (often hidden) AGN, and unusually powerful starburst winds have been suggested to account for these objects. Recent results seem to favor the wind picture, which requires extremely powerful and brief starbursts and perhaps unusually dense surrounding media as well. The GALEX slitless grism mode offers a uniquely powerful way to search for similar objects in windows near z=0.3 and z=0.9. We therefore propose observations of regions of known large-scale density enhancements at z=0.9, where available evidence shows that cluster environments are still very active. Given the sensitivity of the instrument and low background levels, the results would either measure or very strongly limit the evolution of these clouds, and improve our picture of how they relate to the other kinds of objects we can see in the early Universe.

Proposal 77: A FUV Search for White Dwarfs in Binaries

Far UV images covering ~5% of the sky, obtained with the FAUST telescope, have detected several thousand UV sources. Many of these are associated with readily identifiable stellar sources. However, in more than 30 examples, there is a strong excess of UV flux compared what would be expected from the apparent identification. The most likely explanation of this excess is that these otherwise normal stars have a hidden hot subluminous companion, probably a white dwarf. We propose to obtain GALEX grism spectra of 14 of the UV excess objects detected by FAUST to confirm (or not) the present of a white dwarf companion (these are all the fields that do not contravene the bright star limit). From comparison of the far-UV spectral slope with synthetic spectra, we will be able to estimate the temperature of the white dwarf in each case. GALEX is a highly efficient way of searching for binary systems containing a white dwarf component. This work will dramatically extend the sample of known systems, from which spectroscopic or astrometric masses may ultimately be obtained, and provide statistical information on the relative number of white dwarfs in binaries.

Proposal 78: UV Emission in Extended HI Features

We propose to use GALEX to image the UV radiation in systems known to have extended high column density atomic gas far outside the optical disks, in the form of tidal appendages or extended gaseous disks. The data will be used to probe the star formation history far outside the optical galaxy, and even in intergalactic space. GALEX is uniquely suited to detect very faint emission from regions of recent star formation and will allow us to find stellar light too faint to be detected above the night sky background with broad band optical imaging. The FUV/NUV flux ratio provides an excellent clock for young stellar populations and will allow us to identify regions where stars have formed in the past 200 Myr as opposed to current star formation. Combined with HI measures of surface density, shear and velocity dispersion, the data will allow us to test what regulates star formation in these extreme locations, whether disk stability criteria (Toomre's Q parameter) are relevant and whether there is a critical surface density below which no star formation occurs ("Kennicutt Threshold"). Our sample consists of 25 systems mostly from the "HI Rogues Gallery" (Hibbard et al., 2001). Combined with 40 similar systems either targeted or already observed by GALEX, this will provide an excellent data base to study star formation outside of galaxies. A large fraction of the sample consists of merger remnants and almost normal looking early type galaxies, in which we will look for indications of delayed stellar disk formation. As a byproduct we will be able to study in unprecedented detail the star formation history within early type galaxies that are selected to contain neutral hydrogen gas.

Proposal 79: Star formation history of Virgo Cluster galaxies

We propose to image in UV 25 carefully selected Virgo cluster galaxies. The goal is to study the impact of different environmental effects on the star formation history of the galaxies. Our sample is selected from Virgo spiral and peculiar galaxies brighter than 0.2L*, with a range of masses and morphologies in H alpha and HI. The galaxies are located in a wide range of local galaxy densities and show evidence for tidal interactions (harassment), merging and ICM-ISM interactions. By studying in detail individual galaxies which apparently are undergoing trauma of different kinds we hope to elucidate the physical mechanisms that cause the density-morphology, density-luminosity and mass-luminosity relation. Our sample consists of 41 galaxies. Excluding the 16 galaxies that are already done as part of the NGS, we propose to observe the remaining 25 galaxies with GALEX. We already have deep H alpha imaging for the entire sample and are currently carrying out a 15'' resolution deep HI imaging survey with the VLA. By combining H alpha, NUV and FUV images we can trace when, where and by how much the star formation rate has been enhanced or diminished during the last 1-100 Myrs. Since these are the very timescales on which dynamical and gas-gas interactions work, the data will greatly constrain the environmentally-driven evolution of these galaxies.

Proposal 80: Outliers of The Far-Infrared Radio Correlation

We propose to image in UV a sample of 21 galaxies that are outliers of the FIR - radio correlation. Although FIR, radio synchrotron and H alpha emission are all thought to be indirect probes of the presence of young massive stars, the tightness of the correlation, especially between the FIR and radio is surprising. A study of the outliers may help elucidate the physical mechanisms that underlie this correlation. We have identified a sample of 62 star forming galaxies (as evidenced from H alpha) that significantly deviate from the FIR-radio correlation. The galaxies span a range in size (4-30 kpc). One possibility is that the outliers are in a specific evolutionary phase, the beginning or end of a starburst. Early on they will lack radio emission since no supernovae have gone off, at the fading stage they will be bright in radio, since the last population of cosmic rays accelerated by supernovae diffuses out in 10 Myr, but they will lack FIR emission. We have started a multiwavelength study of the different phases of the gas in this sample (H alpha, X-ray and HI imaging) to investigate the nature of these potentially very interesting sources. GALEX can uniquely help to test the young and fading starburst hypothesis. A comparison between the NUV/FUV flux ratio allows us to distinguish regions where stars have formed in the past 200 Myr from currently star forming regions. This is precisely what is needed to identify the early and fading stage of a starburst.

Proposal 81: The Cen-A Jet

GALEX has detected UV (1500 A and 2200 A) emission along the jet of Cen A (NGC5128), at distances up to 40 kpc. from the AGN. The brightest UV emission, aside from the main body of the galaxy, is coincident with two previously known H alpha filaments. A faint plume of UV emission continues beyond the originally identified filaments, clearly associated with ionized gas ( H alpha) along the jet. Some of the UV emission probably originates from (already known) young stars, whose formation was induced by jet-cloud interaction. However, significant amounts of UV emission are detected that are not clearly associated with a jet-cloud interaction-these are likely to be shocked gas or very young stars that have formed as a result of shocks passing through the outer halo of NGC5128. We propose to obtain UV spectra of three distinct environments along the jet: 1) a cloud-free region we believe to be shock-dominated,2) a region of active star formation induced by jet-cloud collision, and 3) a region where the jet is recollimated after disruption. We will compare these spectra to our predictions about the nature of the UV emission in the different environments, and use the results to obtain a clearer understanding of how a jet can influence its host galaxy at large distances from the AGN.

Proposal 85: UV-Bright Probes of Nearby Galaxies

We propose searching for UV-bright [F(1600) > 5E-15 ergs/cm2/s/A] objects behind 100 local galaxies that have the largest angular diameters on the sky and can be observed safely with GALEX. Our aim is to find background sources bright enough to be used by HST at moderate resolution to probe the interstellar medium (ISM) of the galaxy and the interface of the ISM with the intergalactic medium in which the galaxy is found. Short (~1 orbit) exposures using the GALEX grism should reveal sources with the required flux. Based on the number counts of starburst galaxies, blue compact dwarf galaxies, HII galaxies and Liners from the Second Byuraken Survey, and assuming that half of the objects with B <=16-16.5 will have the desired FUV flux, we expect to find ~15-30 probes within 150 kpc of the foreground galaxies.

Proposal 89: GALEX Identification of HeII Quasar Sightlines

The reionization of intergalactic helium is often argued to have occurred between redshifts of about 3-4. Previous studies of HeII Lyman-alpha absorption towards a half-dozen quasars at z>2.7 have demonstrated the great potential of such probes of the IGM, but the currently critically-small sample size has limited confidence in resulting cosmological inferences. The requisite unobscured quasar sightlines to high-redshift are extremely rare, but SDSS provides hundreds of bright, new quasars that are potentially suitable for HeII studies. We propose to use archival GALEX UV imaging data to identify additional new unobscured SDSS quasar sightlines to high-redshift, i.e., those most likely best-suited for detailed HeII studies. Follow-on spectroscopic investigations (e.g., with HST) thereby enabled will measure the spectrum and evolution of the ionizing background radiation, establish the epoch of IGM reionization, and measure the density of intergalactic baryons.

Proposal 91: Search for Young Solar-type Stars

Within 500 parcsecs of the Sun there are thousands of known young stars with ages < 1-3 Myr. Yet within this same volume only a fews tens of stars with ages of 3-80 Myr have been identified. Either we live in a unique epoch in that the Solar Neighborhood out to 500 pc has experienced a singular burst of star formation in the past 3 Myr, or there are thousands if not tens of thousands of unidentified, nearby, intermediate age stars in this volume. Finding these stars is essential since theoretical and observational considerations suggest that planets of all masses are in their final assemblage stages during this evolutionary period. Thus, constructing respectable samples of stars with ages between 3 and 80 Myr is a necessary and essential step for empirical measurement of the evolution of circumstellar disks during the epoch of giant and terrestrial planet formation. The primary difficulty in identifying intermediate age stars is that they are no longer associated with the molecular clouds in which they formed, and they can not be distinguished from ordinary field stars based on optical (BVRI) and near-infrared (JHK) colors alone. However, young stars have active chromospheres and produce ultraviolet emission in excess of the stellar photosphere. We propose an archival program to cross-correlate GALEX with the existing 2MASS and Tycho photometric catalogs that will identify stars with excess FUV and NUV emission. Based on follow-up ground spectroscopic observations of these UV excess sources, we will produce a catalog of intermediate-age stars that will be sensitive to TW Hydra-like objects out to a distance of at least 240~pc. This catalog will be a fundamental resource for studies into the evolution of circumstellar disks and planets around young stars.

Proposal 92: The complete white dwarf population of Praesepe

We propose GALEX far-UV imaging observations of the Praesepe open cluster to identify the complete white dwarf population. In particular, we will identify the missing population of white dwarfs in unresolved binaries with optically bright main sequence companions spectral types K or earlier, via the detection of far-UV photometric excess. These white dwarfs cannot and have not been detected in traditional optical proper motion and colour surveys. Praesepe is the ideal open cluster for this investigation, in terms of size, age, turn-off mass, distance and our detailed knowledge of the normal stellar population. In addition, the identification of a statistically complete white dwarf sample in an open cluster is the best method to determine the cluster's initial mass function.

Proposal 93: Elliptical Galaxy Cooling Flows

The combination of X-ray and far ultraviolet FUSE observations show that some early-type galaxies have the signatures of cooling flows in that there is plentiful hot gas and the OVI UV cooling line is detected, indicating that gas is cooling at about the same rate as the stellar mass loss rate. A consequence should be that these galaxies possess star formation, which has yet to be detected and would have an upper mass limit of about B3. We propose to search for the presence of these young stars by the most prominent indicator of such systems, the P-Cygni line of CIV 1550, produced in stellar winds. If successful, it will be the first evidence for the final state of the cooling gas that is known to be present in individual ellipticals.

Proposal 94: GALEX Grism Spectroscopy of the Open Cluster M67

We propose to obtain GALEX grism spectroscopy of the stars in the intermediate age (4 Gyr) solar metallicity open cluster M67, in order to build a near-UV spectral library for use in spectral synthesis models. Intermediate age populations are known to exist in galaxies ranging from M32 to some of the extremely red objects (EROs) at high redshift. Because near-UV spectroscopy is most sensitive to the main-sequence turnoff, it has the potential to be a powerful age diagnostic, but the near-UV spectra of stars is poorly reproduced by current synthetic spectra due to the strong line-blanketing. Our GALEX spectroscopy will provide empirical NUV spectra for stars along the entire M67 isochrone, and will be particularly useful to interpret observations of intermediate age galaxies obtained in the GALEX grism surveys. The GALEX program complements our HST Treasury Program ``Mid-Ultraviolet Spectral Templates for Old Stellar Systems'' which will provide higher resolution echelle spectra of selected stars, but provide much less coverage along the isochrone. Our proposed GALEX imagery and spectroscopy of M67 will also be used to address several issues concerning binary stellar evolution, including the nature of blue straggler companions, and a search for predicted but missing white dwarfs.

Proposal 95: The UV Variability of Quasars

We propose to use archival GALEX data to measure the time variability of quasars at UV wavelengths. Quasar variability is a well-known but poorly understood phenomenon, and there is currently very little variability information at UV wavelengths, especially shortward of the Ly-alpha 1216A emission line. UV data are important because the peak of the emission from a thermal accretion disk -- which may be responsible for the variability mechanism -- is expected to occur at UV wavelengths. GALEX data are essential because the crucial UV rest wavelength range is obscured from ground-based observations by either atmospheric or intergalactic absorption. We will measure the statistical properties of quasar UV variability by using repeated observations of quasars in almost 200 GALEX DR1 fields, which currently contain over 2000 known quasars from the SDSS. For one field in particular (CDFS_00) the time sampling rate and duration are sufficient to construct lightcurves of individual quasars. Statistical variability measurements derived from the lightcurves are in principle related to the physical parameters of the quasar engine, including the disk size, accretion rate, black hole mass, and gas viscosity.

Proposal 96: GALEX Survey for Subdwarf B Stars

The UV bright, hot subdwarf B (sdB) stars are considered to be core helium-burning stars of 0.5 $M_{\odot}$ with very thin hydrogen envelopes of $M_{\mathrm{env}} \lesssim 0.02 M_{\odot}$, 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. Therefore, more detailed studies with a large number of identified sdB stars are necessary. We propose to carry out (1) a systematic search for \emph{new} sdB candidates in the Galaxy utilizing the GALEX AIS photometry in DR1 with currently available optical and near IR photometry, and (2) ground-based follow-up spectroscopy which will enable us to verify spectral type and luminosity class, and to scrutinize kinematic characteristics. This effort is expected to result in the largest and most complete catalog ever compiled of this stellar class. 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 the formation and evolution mechanism of the stars, and help expand our understanding about dynamical history and structure of the Milky Way.

Proposal 97: GALEX Imaging of Edge-on Spirals

GALEX images of edge-on spiral galaxies (both normal and starburst) have revealed surprisingly bright and extended ultraviolet (UV) halos. Comparison of the UV luminosities and colors with H$\alpha$ observations indicate that the observed UV light is stellar continuum from the disk scattered into our line of sight by dust in the halo. This indicates that the processes that move gas from the disk to the halo affect dust as well, and provides a new way to probe the disk-halo cycle through UV imaging. We propose to obtain GALEX near- and far-UV images of a sample of normal, edge-on spirals, in order to study their UV halos. We will use these data to 1) map the full extent of the extraplanar UV light, and look for variation in UV color with distance from the plane, 2) compare the morphology and luminosity of UV halos with other H-alpha and X-ray data, 3) correlate the properties of UV halos with galaxy properties, and 4) model the properties of the extraplanar dust responsible for the UV halos


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 ~ 60 kpc) system of emission line gaseous filaments. Earlier UV observations by UIT suggested anomalous stellar populations in 6 other early-type Perseus galaxies. A basic goal of the GALEX mission is to use UV imaging to assess the effects of environment on galaxy evolution, but there are no scheduled deep observations of Perseus. Here, we propose to combine 15000 seconds (10 orbits) of GALEX exposures of Perseus to explore this unique cluster environment. We will use the leverage offered by the UV to study the properties of old populations in E/S0 galaxies, star formation in NGC 1275 (especially in the jet-induced mode), and the dependence of star formation histories of late-type galaxies on position in the cluster.

Proposal 99: UV spectroscopy of young star clusters

We propose to take spectra of young star clusters (t < 1 Gyr) in the Magellanic Clouds. These data will serve to improve and extend the calibration of the UV spectral index system for stellar population models, which we have built with IUE spectra from the data bases of Fanelli et al. (1992) and Cassatella et al. (1987). We have developed evolutionary population synthesis models of the most relevant absorption features of stellar systems with ages in the range 1 Myr to 1 Gyr, covering the most important elements including C, Si, Fe and Mg (Nieves & Maraston 2004). The new data will allow the calibration of these spectral indices for different chemical abundances and ages. The calibrated stellar population models will provide an important tool to interpret spectra of high redshift galaxies

Proposal 100: New Solar-Type Post-T Tauri stars

The Taurus-Auriga and Sco-Cen regions of recent star formation were active approximately 1-3 and 10-30 Myr ago, respectively. Over the past several decades several hundred young stars have been identified with each of these regions based on various techniques including objective prism surveys for chromospherically active Ha and CaII emission-line sources, the IRAS survey for objects with substantial mid-infrared excess due to circumstellar dust, and the ROSAT survey for x-ray emission from active young coronae. More recently, deep wide-field optical and near-infrared imaging from the ground has been used to study small portions of these regions (each of which is several 10's of square degrees in total angular extent) with a particular focus on finding young low mass brown dwarfs. Yet the known stellar and sub-stellar populations are far from complete. Each of the above techniques suffers severe selection and completeness effects which bias existing samples. What is needed is a uniform survey designed to detect a characteristic common to all stars younger than several tens of Myr in order to give us a complete picture of the star formation histories of these regions. We thus propose to take advantage of the unique capabilities of GalEx for wide-field imaging in the NUV and FUV at high sensitivity to more fully explore the young stellar and perhaps substellar populations associated with these ''classic'' regions of recent star formation. The chromospheric activity of young stars produces excess flux above their photospheres beginning in the optical U-band and extending to the NUV and FUV. We will combine GalEx data with existing 2MASS, Tycho, and our own ground-based U, R, I surveys of these regions to identify new chromospherically active young stars for confirmation via follow-up optical spectroscopy. Due to the 3-80 Myr age range of our selected objects this program is highly relevant to the planet formation and early evolution of planetary systems goals in NASA's Origins Roadmap.

Proposal 102: UV properties of moderate redshift galaxies

We propose to use archival data from the GALEX Data Release 1 to study the UV properties of moderate redshift (0.2"<"z"<"1.5) galaxies in combination with deep HST imaging. We will concentrate on the Ultradeep GALEX imaging data (UIS) centered on the Chandra Deep Field South, where HST imaging is available over 1/4 square degree. Our main goals are: 1) determine the correlation of unobscured star-formation (from GALEX) with morphogical type and merger activity (from HST); 2) correlate the changes in the slope of the UV continuum with the spatially resolved color distribution within HST images; 3) search for blue cores in early-type galaxies as function of z and make a definitive link between them and star formation activity; 4) investigate source confusion arising from multiple HST-selected galaxies within single GALEX beams. Assess the importance of source-blending problem which has implications for all the deep GALEX surveys.

Proposal 104: GALEX Observations of Long-Period Comets

Long-period comets are carriers of the most pristine examples of material left over from the formation of the solar system. The study of these objects is therefore foundational to our understanding of the early solar system. Except for in-situ studies of comets, which have yet to be made for long-period comets, remote-sensing studies, primarily of coma emission lines, are the only way to measure the composition of these objects. Owing to their ephemeral nature, observing opportunities for long-period comets are rare, particularly in the vacuum ultraviolet. GALEX, with its wide field of view and spectro-imaging capabilities over a broad range of the vacuum UV, is an ideal instrument for the study of cometary coma emission lines. Since the relative brightness and radial extent of coma lines depends on the heliocentric distance of the comet nucleus, multiple observations, spaced days or weeks apart, are necessary to more fully understand coma dynamics and the underlying intrinsic nuclear abundances. Our team, which includes expertise in UV observations of comets, coma modeling, and sophisticated data analysis techniques, offers to help the GALEX G.O. and P.I. teams coordinate observing campaigns of any long-period comets that may be discovered in the 2004-2005 time period.

Proposal 108: Measuring of Lyman continuum absorption

We will measure the amount of Lyman continuum absorption in the universe at 0.5 < z < 2.5 approximately one hundred time more accurately than published results that have errors of 30%. We work with the GALEX FUV and NUV fluxes for 6000 known QSOs in the GALEX DR1. We will compare these fluxes to those that we expect using template spectra that we match to published optical and NIR fluxes, especially from the SDSS and AAT 2dF. We expect to detect approximately 2000 Lyman limit absorption systems (LLS) towards these QSOs from the flux that they remove from the GALEX bands. Published analyses use approximately 17 LLS at these redshifts from HST spectra. We will derive the LLS density, per unit redshift, which is a key input to calculations of the intensity of the cosmic UV background. We also obtain some information of the distribution of the H I column densities of the LLS. The UV background is required to understand the ionization of the intergalactic medium (IGM) and the gas in the outer regions of galaxies that causes QSO absorption lines.

Proposal 109: A UV Imaging Survey of the SAURON Sample

Much information about the formation and evolution of galaxies can be gleaned from probing their mass assembly and star formation histories through combined dynamical and stellar population studies. The SAURON Team recently surveyed the two-dimensional stellar/ionized-gas kinematics and stellar populations of a representative sample of 72 nearby early-type galaxies. The survey revealed a rich diversity in the kinematics, discovering numerous central disks and kinematically decoupled cores. The limited V-band linestrength diagnostics indicate that most galaxies have uniform and old stellar populations. By combining far-ultraviolet (FUV) and near-ultraviolet (NUV) imaging observations from GALEX with existing SAURON data, we aim here to 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. In particular, these observations will reveal the spatial distribution of the enigmatic ''UV-upturn'' population. Of particular interest is whether star formation is closely associated with the kinematic (sub)structures detected by SAURON. Other important goals include identifying the orbital families populated by young stars, constraining their migration patterns, and testing the reliability of linestrength-based methods to detect young populations. The combined SAURON and GALEX data will provide by far the best measurement of the relative roles of merger-induced and passive star formation in early-type galaxies today, and they will give us a privileged glimpse into the future of those objects.

Proposal 110: UV Investigation of Quasars

We propose to use archival GALEX data to supply the UV component of the spectral energy distributions (SEDs) of a large number of quasars contained within the Spitzer First Look Survey (SFLS) area. The SFLS affords a unique opportunity to combine multi-wavelength data from wide-area surveys covering the radio, IR, optical, UV, and X-ray regimes. The GALEX data are essential since the peak of the typical quasar SED is expected to lie at UV wavelengths (shortward of Ly-alpha 1216A), which are inaccessible from the ground due to either atmospheric or intergalactic absorption. There are 40 spectroscopically confirmed SDSS quasars inside the overlap of the SFLS and GALEX DR1 areas, and over 3 times as many highly reliable photometrically identified quasars in the fainter SDSS imaging data. The dataset will extend our knowledge of the SEDs of quasars to higher redshifts, lower luminosities, and redder intrinsic colors. The unprecedented sample of normal quasar SEDs will contribute significantly to our understanding of the physical processes that drive quasars, and serve as a basis for comparison with unusual or obscured quasars.

Proposal 113: The Nova - Dwarf Nova Intimate Connection unmasked by GALEX

In a totally unexpected, serendipitous discovery, GALEX has demonstrated that the dwarf nova Z Cam displays a shell of ejected matter nearly a degree across. Why? Dwarf nova are not believed to be ejecting matter. We think that it's either because Z Cam is an ancient classical nova, or because dwarf novae really do eject shells of matter, contrary to the ''party line'' view of these objects. We propose to image several classical and dwarf novae to determine if all (or most) dwarf novae have UV-prominent shells; if so, then the standard model of dwarf novae is grossly incomplete and must likely be discarded.

Proposal 114: Stellar Archaeology: Searching for High-Ionization Planetary Nebulae with GALEX

Diffuse, extended planetary nebulae (PNs) are expected around hot, low mass central stars. Because of their low surface brightness, these highly evolved nebulae are difficult to find in optical searches. The high temperatures of their central stars, coupled with the low density of the envelope, implies that much of the photoionized nebula is in a high-ionization state. Photoionization models of old PNs, using realistic density structures calculated by hydrodynamic models, show that C IV 1549A and He II 1640A are among the strongest lines emitted -- much brighter than any optical lines. Therefore, the ultraviolet is the optimal bandpass in which to detect this important population of PNs. We propose to use GALEX to search for evolved PNs around a carefully selected sample of potential central stars. We also propose to observe the recently discovered nebula around PG 1034+001, a member of this important population of PNs. The discovery of new PNs is the primary goal of the project. The observations will also yield the morphology of the UV emitting gas and the sum of the C IV and He II fluxes. When compared with photoionization models, these measurements will constrain the properties of the nebulae. Its field of view, sensitivity, and wavelength coverage make GALEX the ideal instrument with which to conduct this search for old planetary nebulae that at other wavelengths could easily remain undiscovered.

Proposal 115: The Ultraviolet Spectral Properties of Blazars

We propose a pilot project to obtain UV spectra of a well-defined sample of BL Lac objects with GALEX. Our aim is to conduct a systemativ survey for broad UV emission, by far the strongest line in these weak-lined AGN. This will allow us to estimate the unbeamed power and thereby test unification models, particularly those that tie broad emission line luminosity to multiwavelength SED shape. The proposed targets are the UV-brightest BL Lacs for which Ly alpha line emission could not be confirmed with IUE or HST. We have selected objects with z>0.11 to ensure that Ly alpha falls in the wavelength range GALEX can observe. By combining the results with archival IUE and HST data for flat-spectrum radio quasars, which represent higher-luminosity blazars, we will be able to span the full range of blazar types, allowing a complete statistical assessment of the class and an unprecedented comparison of emission line luminosities across orders of magnitude in jet kinetic power. These observations will also yield redshifts for four objects without known z.

Proposal 117: GALEX Grism Spectroscopy of the Globular Cluster Omega Centauri

We propose to obtain GALEX FUV-only grism spectroscopy of the hot stars in omega Centauri, the most massive globular cluster in our Galaxy. Previous UIT imagery of omega Cen showed that it contains about 2000 hot horizontal branch (HB) stars, and we estimate that GALEX spectra can be obtained for about 500 of these stars in the outer regions of the cluster, including about 50 of the hot ``blue hook'' stars discovered with UIT. The blue hook stars appear to be both hotter (35,000 K) and less luminous in the UIT color-magnitude diagram than predicted by canonical HB models and, indeed, are unexplained by standard evolutionary theory. Brown et al. (2001) have suggested that the blue hook stars are the progeny of stars which mixed their surface hydrogen into their hot He-burning interior during a delayed helium flash subsequent to leaving the red giant branch. This ``flash-mixing'' results in a hot hydrogen-deficient star with a typical surface abundance of 96% He and 4% C by mass. The GALEX spectral region includes the strong lines of C III 1426, 1578 A, C IV 1550 A, and He II 1640 A which will allow this predicted carbon and helium enrichment to be detected. These observations will therefore provide a crucial test of the Brown et al. flash-mixing hypothesis and will determine if flash mixing represents a new evolutionary channel for populating the hot HB. The GALEX spectra will also address other questions concerning the hot HB in omega Cen including (1) the metallicity distribution of HB stars with 9,000 K < Teff < 11,000 K, (2) the effect of radiative levitation on the UV spectra of stars with Teff > 11,000 K, and (3) the origin of the subluminous HB stars found in the UIT photometry with 15,000K < Teff < 30,000 K.




Responsible NASA Official: Susan G. Neff
J.D. Myers

NASA Privacy, Security, Notices