Abstracts for Accepted Cycle 2 Programs
VIEW AN ABSTRACT FROM CYCLE 5
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We propose an archival search of the GALEX UV data-base to reveal the variability in FUV and NUV magnitudes of many known (and newly discovered) quasars & AGN. This UV variable source list can then be used to establish correlations and relationships (with redshift, luminosity etc derived from the SDSS DR5) that will further our understanding of these enigmatic objects. Further correlations will be explored by examining quasar/AGN variability in sub-samples separated by radio loudness, x-ray brightness, spectral index, and emission line parameters. An important by-product of this study will be identification of the most UV variable quasars and AGN. These sources will be prime targets for future reverberation mapping observations.
We propose to obtain 1.5 ksec GALEX observations of a set of nearby, low mass galaxies detected in the HI line by the currently ongoing Arecibo Legacy Fast ALFA (ALFALFA) survey found in diverse environments: the Leo Group of galaxies and very local density regions. The targets are among the lowest HI mass ALFALFA detections, and their narrow line widths imply low dynamical masses. The proposed observations complement on-going Cycle 3 (GI3-84) and Cycle 4 (GI4-42) SNAP observations of ALFALFA objects selected from earlier versions of the ALFALFA catalog and are specifically designed to probe the extremes of intergalactic environment. As members of the ALFALFA team, we are undertaking a multiwavelength study of the lowest mass ALFALFA detections to determine the cosmic abundance of low mass gas-rich systems, their distribution and their characteristics as a galaxy population. In combination with optical broad band and H-alpha imaging, NIR/FIR and radio continuum fluxes, and HI line measures (fluxes, redshifts and widths), GALEX UV observations will yield star formation rates and ages and trace the sites of the youngest stellar populations, even in systems where the current/past star formation activity has been very low. In combination with GALEX archive observations of the Virgo Cluster region, the proposed program will yield a sample of sufficient size to allow the identification of trends in star formation within the Virgo Cluster and Leo Group environments and will explore a set of objects which may not have experienced interactions with other galaxies over the Hubble time.
Two cataclysmic variables containing pulsating white dwarfs underwent outbursts in 2007 (GW Lib and V455 And). As we know outbursts heat the white dwarfs by more than 10,000K and they gradually cool to their quiescent temperatures over the course of about 3 years, these two objects present the first unique opportunity to follow the pulsation spectrum of a white dwarf as it cools on much more rapid timescales than evolutionary ones for single white dwarfs. As these 2 objects cool, they should re-enter their instability strips and we can witness changes in the driving mechanism and detect modes that are excited by the T changes. Our 2008 ground-based data on GW Lib has shown a new pulsation at a longer period than at quiescence. The data in 2009 will be combined with our time for GW Lib in Cycle 4 and our DOT time in 2007 to follow the long term cooling of GW Lib and obtain similar information on V455 And. The higher pulse amplitude in UV vs optical and the time-tag mode means that GALEX can provide optimum data over the optical. Data on both systems will provide an important contrast in how the white dwarfs react to an outburst, as GW Lib at quiescence has a hot white dwarf far outside the normal instability strip for non-accreting white dwarfs, while V455 And is cool and inside this strip.
This archival proposal will study, for the first time, the UV properties of a large number of BL Lacs. BL Lacs are rare AGN viewed nearly along the axis of a relativistic radio jet; this orientation yields strong (Doppler boosted) multiwavelength emission. BL Lacs are thus excellent probes of AGN jet physics. Such a UV investigation is long overdue and is now possible because 1) BL Lac sample sizes have ballooned from dozens to hundreds of objects over the past 10-15 years; and 2) the large area coverage of GALEX serendipitously includes many of these extremely rare objects. We preliminarily identified a subset of about 400 BL Lacs from the SDSS that also appear in the GR2/3 GALEX archive; we expect this number to increase by at least a hundred after we correlate to GR4 and as we expand our SDSS BL Lac catalog. Even this subset of 400 UV-detected BL Lac objects is larger than most entire BL Lac samples. The UV is insensitive to contamination from BL Lac host galaxies, making the UV the best probe of the jet at moderate frequencies for certain objects. We will compute basic UV properties from GALEX data (e.g., spectral indices, fluxes, etc.), constrain the UV luminosity function, and investigate claims that the peak frequencies of BL Lac SEDs are anti-correlated with luminosity. The sheer number of BL Lacs with GALEX data coverage will place excellent constraints on the UV character of BL Lac objects, especially on the proposed anti-correlation of peak frequency with luminosity. The presence or absence of an anti-correlation will influence models of jet emission mechanisms.
Supernova (SN) explosions play a pivotal role
in triggering, driving, and (later on) inhibiting further star formation in
galaxies. In fact, the combination of new observations and refined modelling shows that the little-understood and poorly
constrained contribution of SNe to galaxy evolution processes (often hidden
under the generic name of ``feedback'') is probably the weakest link in our
understanding of structure formation in the Universe. Setting observational
limits on the rate, environments, and energy output of high-redshift SNe is
therefore one of the main science drivers of recent Hubble Space Telescope
(HST) legacy programs, as well as of future missions like the James Webb Space
Telescope (JWST). However, observations of high-redshift SNe in the optical (by
HST), or in the near-IR (by JWST), actually sample the rest-frame UV of these
objects. Thus, proper interpretation of these observations requires knowledge
about the UV properties of SNe. Such UV data are also powerful probes of the SN
environment, progenitor structure and explosion mechanism. Unfortunately, UV
spectroscopy of local SNe of all types, which can only be obtained from space,
is scarce. Previous efforts using HST and IUE were focussed on a single SN sub-type,
The appearance of galaxies changes according to their observed rest-frame wavelength, particularly when comparing the UV to the optical. This can lead to mis-classifications of galaxies observed in the UV, which is of particular concern for high redshift studies where light emitted in the UV is observed at wavelengths up through the infra-red. An understanding of this effect with a statistically large sample of nearby galaxies is needed in order to apply corrections to the morphologies of these high redshift galaxies. This is essential to studies of galaxy assembly and evolution. We propose to conduct the largest and most precise study to date of the wavelength dependence of nearby galaxy morphologies with all available deep GALEX archival observations. This "morphological k-correction" will be measured through the change in galactic structure with wavelength as parametized by the CAS indices (Concentration, Asymmetry, and Clumpiness).
GALEX legacy data products include shallow and deep field surveys that at low redshift sample a range of local and global environment, but which only sample a range of local environments at higher redshifts. We propose a targeted survey of high-overdensity fields at intermediate redshift to complete the legacy value of GALEX for the study of galaxy evolution as a function of environment. The EDisCS sample of galaxy clusters is uniquely suited because it, among samples publically available, is the only to provide a fair match to the internal velocity dispersion distribution of local clusters while also providing deep optical and near IR ground-based photometry, optical spectroscopy, and, for portions of the entire survey, Spitzer IRAC and MIPS photometry, HST ACS imaging and XMM-Newton observations, all of which are, or will soon be, entirely public. Our science focus is on measuring the current and recent star formation rates of cluster galaxies to address issues regarding the modulation of star formation by the cluster environment.
We propose to use GALEX to image the neighboring clusters A1763, A1770, and the two filaments connecting them (all at a redshift of 0.23). We recently discovered these two filaments in a wide-field Spitzer observation of A1763 and have been able to confirm their existence with spectroscopic follow-up surveys. The proposed GALEX observations will allow a homogeneous coverage of both filaments as well as the two cluster-core galaxies. The proposed GALEX images will be used for the measurement of UV extinction corrected star formation rates in galaxies belonging both to the clusters and to the filaments - estimates which are crucial in the understanding of galaxy evolution in and around clusters. Additionally, the data will be essential for the analysis of the spectral energy distribution of the galaxy sample; in particular, we will be able to separate type-1 AGN from "normal" galaxies.
Last year a FUV only emitting bow shock and turbulent wake extending 2 degrees (4 pc) behind the Asymptotic Giant Branch (AGB) star Mira was discovered in GALEX survey images. It came as a surprise that Mira, the prototype for Mira-class long period variables and the nearest AGB star, kept such an enormous feature secret despite being heavily studied for the past 400 years. Even more surprising is the revelation that the FUV can provide crucial information about the mass-loss history of a cool and dusty AGB star by tracing the interaction between its circumstellar envelope (CSE) and the ambient interstellar medium (ISM). The FUV emission is understood to be fluorescence from molecular hydrogen (H2) that has been collisionally excited by energetic electrons within the hot bow shock gas. Typical space velocities and wind speeds of AGB stars suggest that this phenomenon may be common. We have compiled a catalog of AGB stars within 500 pc which contains reliable proper motions, radial velocities, distances (hence space velocities), wind velocities, and mass-loss rates. From this information we are able to estimate the physical size and strength of CSE-ISM shocks and wakes. We propose a UV survey of nearby AGB stars selected as likely candidates to produce H2 fluorescence in order to investigate the frequency and parameter space of this phenomenon - a survey only possible with the sensitivity and large field of view of GALEX.
.\ The core of the Coma Cluster is one of the densest environments in the low-redshift universe and a vital laboratory for studying galaxy evolution. As the archetypal rich galaxy cluster, Coma has been extensively studied at all wavelengths. Our HST Coma Treasury Survey, and associated wide-field spectroscopic and imaging follow-up work, has assembled a powerful dataset for understanding galaxy evolution in the cluster environment. \ Until now, however, the core of Coma has not been observed with GALEX, due to UV-bright stars in the field. Since Cycle 3, the detector safety limits have been relaxed such that this important observation is now allowed in "petal pattern" mode. \ \ Here we request deep imaging (30 ksec) of a single pointing at the center of the Coma cluster, to complement a similarly-deep exposure we obtained for an off-center field in Cycle 2. The data will be used (1) to investigate the faint end of the UV luminosity function in a very dense cluster environment, for comparison with outer parts of the cluster (2) to test models for the formation of passive dwarf galaxies in clusters, using the UV/optical color-magnitude relations and (3) compare quantitatively the colors with extensive high-S/N spectroscopy for giant and dwarf passive galaxies in Coma. \ \ The observations are supported by extensive HST and ground-based optical/near-IR imaging (including deep u-band), and by a comprehensive MMT/Hectospec redshift survey of thousands of potential cluster members.
The 9th magnitude F2 star HD 109962 is a single-lined spectroscopic binary with a 0.893 day period. It may be the most massive dwarf nova system yet discovered. In outburst the excess luminosity source (the hot inner accretion disk) is totally eclipsed. Outside of the outburst, GALEX spectra will yield the temperature of the secondary, expected to be a hot white dwarf. This is necessary for a full characterization of the system. Observations of this system will help us to understand the accretion process in and evolution of cataclysmic variables wherein the mass donor has a very thin convective zone.
Detailed studies of HeII Lyman-alpha absorption toward a half-dozen quasars at 2.7<z<3.3 confirm the great potential of helium Gunn-Peterson studies of the IGM, but the critically small sample size limits confidence in cosmological inferences. Although the unobscured quasar sightlines to high redshift are extremely rare, SDSS now provides 9000 confirmed z>2.8 quasars potentially suitable for HeII studies. Under past programs, we cross correlated SDSS DR6 with GALEX GR2/GR3 to identify 200 higher confidence (plus 200 less confident) quasars at z=2.8-5 that are likely bright in the far-UV restframe. HST reconnaissance UV prism spectra of 22 SDSS/GALEX quasars confirm 11 as detected in the far-UV, with 8 having flux down to their HeII breaks. Considering just the higher confidence set, our HST measured efficiency for SDSS/GALEX selection of far-UV bright quasars is 90%, with 70% efficiency for selecting quasars suitable for HeII studies. We propose to expand our successful archival program to include GALEX GR4 and post-DR6 SDSS surveys to yield a catalog of 500 likely far-UV bright z>2.8 quasars. The order(s) of magnitude increase in selection efficiency and numeric yield of new sightlines will yield a community resource list of the best (UV-brightest at given redshift) quasars for future HeII UV spectral studies. Nearly all will be accessible to quality UV spectra with HST (COS or STIS), with the brightest comparable in UV flux to the most famous HeII quasars. Ultimately, our sample will enable optimized, quality UV spectral studies that can average over individual object pathology and cosmic variance to confidently assess: the spectrum and evolution of the ionizing background, the evolution of IGM HeII opacity, the onset and completion epochs of helium reionization, and the density of IGM baryons.
The Wide component of the CFHT Legacy Survey is an ambitious, 219 sq. degree imaging survey carried out with Megacam. It is currently in its final semester, and much of the data is already publicly available. The survey itself consists of five optical filters, reaching a depth of r=25.9, and includes a wide variety of other data including the XMM-LSS, VVDS spectroscopy, and Spitzer infrared observations. However the fields are only partially (25%) covered by GALEX observations to a depth useful for studies of distant galaxies. We propose a 150 orbit GALEX Legacy survey to complete coverage in all 4 fields. From the CFHTLS data processed so far (121 sq. deg.) we have constructed an unprecedented sample of nearly 500 uniformly selected, massive clusters at 0.2<z<0.45; this sample will exceed 700 when the full survey is analyzed. We will use the GALEX data to measure the dependence of star formation on environment in the environs of these clusters. Our large sample allows us to explore cluster-to-cluster variations and the galaxy populations within the low density groups and filaments that surround these systems on very large scales. However the data will have much broader appeal to the global community and thus we propose these observations as a legacy Proposal, and waive all proprietary rights. Full coverage of these exquisite fields will ensure that the impact and Legacy of GALEX will continue well into the future, and beyond its mission lifetime.
A deep, high-resolution, Halpha image of the classic cooling-flow cluster Abell 1795 was recently obtained with the Maryland-Magellan Tunable Filter on the Baade 6.5m telescope. The well-known, 50-kpc long, Halpha/X-ray emitting filament south of the cD galaxy breaks up into two intertwined "strands" that can be traced all the way into the central galaxy. The origin and energy source of this intriguing filamentary structure are unknown. We propose to use the imaging mode of GALEX to search for young stars and determine their contribution to the ionization/excitation of this filament. The UV-inferred star formation rate will be compared with the mass deposition rate derived from the published CXO and XMM-Newton data to constrain the origin of the filament and the role played by the radio source in the cD galaxy.
Early-type galaxies have a hot X-ray emitting
interstellar medium, along with cooler gas that is detected through optical emission
lines or through dust emission and extinction. Whether or not the cooler gas is
a consequence of modest cooling flows, it does not accumulate, as large amounts
of mass are not present. The implication is that the cool gas is consumed in
low-level star formation, a phenomena that has received little study due to
technical difficulties that are overcome uniquely by GALEX grism observations.
The best available indicator of star formation is the P-Cygni line of CIV 1550 A, produced in
stellar winds of
With recent advances in modern technology, we are able to peer further back into the Universe then ever before. One of the many exciting discoveries was the existence of Lyman alpha galaxies. Due to their large Lyman alpha equivalent widths, these objects could be some of the first galaxies in the Universe. Over the last decade, we have learned much about these objects at high redshift, including the fact that they may not be primitive galaxies at all, as many contain significant amounts of dust. While Lyman alpha emission has been detected from galaxies locally (i.e. Haro 11), and as low as z ~ 2.4, there exists a vast gap in cosmic distance where we know nothing about these objects. A recent study (Deharveng et al. 2008) has used GALEX to discover ~ 100 Lyman alpha galaxies at 0.2 < z < 0.35. We propose to use these GALEX data to study the stellar populations of these objects, specifically searching for signs of evolution from their high redshift counterparts. We will then test theories of Lyman alpha escape by obtaining ground based spectra and comparing the Lyman alpha line strengths in the GALEX data to outflow velocities derived from interstellar lines from the optical data, searching for evidence that outflows help the escape of Lyman alpha photons. The optical spectra will also allow us to study the Lyman alpha / H-alpha ratios, which are an important constraint of ISM geometry. These two studies together will enable us to obtain a picture of metallicity evolution across redshift, as well as learn about the interstellar kinematics, which we cannot yet do at high-redshift. Our knowledge of LAEs at high-redshift is incomplete due to data limitations,thus we need to study these objects at low-redshift where we can study their detailed properties. As direct measurements of the Lyman alpha line and rest-frame FUV continuum are crucial to both of these studies, GALEX data is required for the completion of this proposed work.
We propose to study all ultraluminous and luminous IR galaxies (LIRGs) with Lir > 10^11.4 Lsun 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 18 objects, which will be combined with archival data from our Cycle 1 program, the NGS, and the AIS. In addition, these data will add to the Great Observatories All-Sky LIRG Survey (GOALS), which already includes Spitzer, HST, Chandra, VLA, and optical data on all of our targets. Primary questions to be answered include: How does the IRX-beta relation change with luminosity? How does the age of the nuclear starburst correlate with merger stage and luminosity? What are the properties of local LIRGs which are counterparts of the Dust Obscured Galaxies seen at high redshift? By combining this proposal with the archival data, we will have complete, high quality UV data for all GOALS LIRGs observable by GALEX with Lir > 10^11.4 Lsun. These galaxies form an ideal sample for studying interactions and star formation in the local universe.
H-alpha dots are point-like H-alpha emission line sources, likely isolated HII regions or dwarf star-forming galaxies, that are spatially located near larger galaxies. Our goals via this pilot project are: 1) to determine the stellar mass and star-formation rates of these objects; 2) to utilize this information to determine whether the sources are HII regions or dwarf galaxies and whether they are physically related to the large, nearby galaxies; and 3) to assess the feasibility of observing a large number of these sources in the future.
We propose to search for the GALEX archive for UV counterparts to 6,500,000 stars with proper motions >20 mas/yr. A reduced proper motion diagram will be used to identify white dwarfs, yielding an estimated census of 100,000 white dwarfs within 250 parsecs of the Sun. The census will notably include large numbers of high-velocity white dwarfs from the Galactic thick disk and halo. The resulting database, to be made available to the astronomical community, will provide a formidable dataset to study the distribution and kinematics of white dwarfs in the vicinity of the Sun.
We propose spectroscopic observations of the HDF-S, one of the best studied fields on the southern sky, using the GALEX slitless grism spectrograph. Combining the data with optical spectroscopy will enable us to derive luminosity weighted ages for a sample of Low Surface Brightness galaxies by fitting model spectral energy distributions. With this study we will test assumptions that LSB evolve on fundamentally different tracks compared to their High Surface Brightness counterparts. The emission lines in the UV allow predictions of abundances using emission line diagnostic. Beside informations about metallicities and ionization stages, the abundances give also independent information about star formation histories. We also plan to study dwarf galaxy populations at intermediate redshifts up to z~0.2. The spectroscopic UV information will enable us to derive reliable Star Formation Rates and to better characterize the nature of very blue and small dwarf galaxies they found exclusively in the redshifted sample. We will address the question if these galaxies undergoing their first significant starburst at redshifts around 0.2. In addition the spectroscopic data allow for the identification of bright QSOs at low and intermediate redshift in the field and give the opportunity to search for Damped Lyalpha and Lyman Limit Systems. With the variety of available space- and ground-based data for the HDF-S, UV spectroscopy will create the opportunity for a wide use within the astronomical community.
We propose NUV + FUV imaging of the blue S0 galaxy CGCG 065-002, which displays an unusual morphology characterized by an abundance of resonances and related structures including bright blue rings and an apparent "super-bar" in the outer disk, as well as a blue dwarf companion. The observed morphology of this galaxy may represent a short-lived evolutionary phase that many low-mass, field E/S0 galaxies experience as part of a process of rebuilding extended disks. Examining recent star formation in this galaxy and its companion will allow us to understand what drives gas to flow inward, condense, and form stars in E/S0 galaxies during the disk-rebuilding phase. GALEX has proven the instrument of choice for detecting new disk growth in the form of extended UV emission, including XUV disks in low-mass E/S0s (GI3-0046). As a uniquely hyper-resonant galaxy, CGCG 065-002 offers clues to how such disks form. We seek to trace its extended star formation, the axial ratio of its outer disk (to verify the super-bar), and any tidal features that may demonstrate a companion interaction. GALEX FUV-NUV colors will also provide a vital chronometer for young stellar populations up to a few 100 Myr, enabling us to test for a causal link between starbursts in the primary and its companion. Combining GALEX imaging with ground-based multiwavelength observations of the target, we seek to construct a coherent picture of the role of resonances in driving disk regrowth.
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 our previous 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. Our proposed study builds on our well-validated criteria for selecting low-mass stars from all-sky catalogs and identifying the very youngest members out to 100 pc. We will acquire follow-up optical spectroscopy of GALEX-selected candidates to confirm their youthfulness, 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. As a result, our census of young low-mass stars near Earth will provide a rich set of targets for intensive ground-based and space-based follow-up studies to understand the planet formation process in the low-mass stellar regime. Our objectives are directly related to NASA's goals of detecting and understanding extrasolar planets and their formation.
Understanding the progenitors of
We propose a MIS survey (59 pointings) with GALEX of the 108 square degrees covered by the Galaxy And Mass Assembly survey (GAMA). GAMA is a multiwavelength (ugrizYJHK FIR/submm) imaging, spectroscopic (370-880nm and 21cm HI) survey of the nearby galaxy population (125k galaxies out to z~0.25), covering 144 sq. deg. of the equatorial sky using the 3.9m Anglo-Australian Telescope (AAT) Dedicated observations of the fields are underway or guaranteed with AAT (66 nights), UKIRT (30 nights), VST (60 nights) VISTA (45 nights) Herschel (200 hours) and the Australian Square Kiliometre Array Pathfinder ASKAP (equivalent one year observing time). Redshifts have already been obtained for 50,271 galaxies in the initial observing campaign during March 2008, The spectroscopic depth of GAMA is well matched to the imaging depth of GALEX in MIS mode for normal spiral galaxies, providing an optimum basis for the study of a deep volume-limited sample of the local population of spiral and dwarf galaxies in the UV to test the CDM paradigm. In particular, the very high redshift density (12 x that of the SDSS) is ideal to probe structure traced by UV-emitting galaxies on the sub Mpc scales on which on which dark matter halos virialize and merge, and baryons decouple, collapse and eventually start forming into the stars detectable in UV light by GALEX in, and around the periphery of, the complex visible structures that are galaxies. In particular, we will be in a position to compare and contrast the UV LF of field galaxies with the LF of galaxies in clusters and groups as a function of the depth of the gravitational potential in the parent dark matter halos, as probed by the dispersion of galaxian velocities in the groups and clusters. This will constrain the efficiency of conversion of baryons into stars as a function of halo mass.
Mergers and close-passages between gas rich galaxies can result in the formation of long HI/stellar streams. The tidally induced star formation and gas concentrations can result in the creation of tidal dwarf galaxies (TDGs). TDGs may contribute significantly to the dwarf galaxy population, by far the most common galaxy type in the current epoch. We have discovered one of the longest known tidal streams (500 kpc) in the NGC 4535/DDO 137 system. We propose 3 ksec FUV/NUV images centered on the stream and its five TDGs. We will readily detect faint/low mass star forming regions (~2E-17 erg s-1 cm-2 A-1) to 5-sigma. The GALEX observations are a unique opportunity to undertake a sensitive and comprehensive study of tidally induced star formation, dwarf galaxy formation and inter-galactic enrichment in this system.
We propose to construct a map of the strength of the 2175 A dust feature in the Milky Way in the direction of the Galactic cap. The origin of the 2175 A bump is an open question, with some type of carbonaceous grains being the leading suspect. The strength of the 2175 A bump is known to vary significantly from being a pronounced feature in the Milky Way to being nearly absent in the SMC. Even within the MW the strength of the feature is known to vary significantly across different lines of sight. A map of 2175 A feature strength would be extremely helpful for accurately dust correcting the UV flux of both Galactic stars and external galaxies. In addition such a map may provide insights the nature of interstellar dust and the role that it plays in Galactic structure and evolution. Convolving extinction models with stellar template spectra shows that for a fixed spectral type the GALEX FUV-NUV and Swift UVOT uvw2-uvm2 color indices are sensitive to the strength of the 2175 A feature, while SDSS u-g and UVOT uvm2-uvw1 colors are sensitive to the level of extinction in the optical. We propose to create a 2175 A map using archival SDSS photometry and spectroscopy to accurately determine the spectral types an optical extinction of individual hot stars and then determine the 2175 A bump strength with the archival GALEX FUV-NUV colors from the All-Sky Imaging Survey and the Galactic Cap Survey. UV data from Swift UVOT will be used to calibrate the method on the comparatively small area covered by both UVOT and GALEX and then applied across the full Galactic cap with the large area GALEX surveys. We estimate that there are 1.6 usable stars per square degree which will set the resolution scale of the map.
HST imaging has shown that the dynamics and symmetry of mass-loss starts to change dramatically during the late-AGB phase of stellar evolution, 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 UV that the companions (which are generally likely to be hotter) outshine the former. In Cycle 1, we succesfully used GALEX's FUV/NUV imaging capability to search for hot companions in a small sample of cool AGB stars. We found FUV excesses in almost 40% of our 21 objects, and showed that these most likely arise either due to one or both of photospheric emission from a hot (>7500K) companion, or an accretion disk around the latter. We now propose to distinguish between these alternative scenarios by obtaining GALEX UV grism spectra of these objects. We will fit the detected NUV and FUV continuum using the modelling tools we have already developed to remove any contribution of the cool primary, and derive the temperature of the emitting region. Emission lines, if detected, will provide constraints on the physical parameters of the accretion disk such as the (electron) density, emission measure, and thus the emitting volume. We should also detect emission in the 2800 Ang (Mg II h & k) line - the only line that may come from the cool primary arise (due to chromospheric emission), and thus help model its contribution to the NUV broad-band fluxes derived from GALEX images.
We propose deep GALEX FUV and NUV imaging, with 4.5 ksec (3 orbit) exposures, of an additional 10 sq. degrees of the region of sky that will be monitored by the KEPLER satellite. In Cycle 4 we were awarded similar observations of 20 GALEX fields and these new observations represent the remaining unconstrained regions that are observable by GALEX within the Kepler FOV. The Kepler Mission will observe a 105 sq. degree area, essentially continuously for a minimum of 3.5 years looking down the Orion spiral arm in the direction of Cygnus/Lyra, with the goal of measuring the properties of hundreds of transiting extrasolar planets. To achieve this goal Kepler will observe well over 100,000 stars in broadband optical light. Observations of significant numbers of non-prime-science targets (stars, AGN, or whatever types of interesting objects people propose) will be possible through the Kepler GO program. We will use our GALEX images to identify previously unrecognized active stars in the V=9-15 range by their FUV excesses compared to inactive stars. MANY other objects that could be of interest to the wider astronomical community will be present in these fields and available to Kepler GOs for the planned annual proposal opportunities.
We propose moderately deep GALEX observations (6 ksec) of eighteen gas-stripped Virgo Cluster spiral galaxies. These observations will give a complete sample of strongly stripped, highly inclined (i>70 degrees) Virgo spirals brighter than magnitude 16. Optical imaging and HI mapping show that these spirals all lack dust and gas in their outer disks, presumably due to ICM-ISM interactions. GALEX UV observations will provide critical information on how these interactions have affected recent star formation in the galaxies. The GALEX FUV and NUV data, particularly when combined with our existing multi-wavelength data set including broadband optical, H-alpha, and Spitzer IR imaging, and optical spectroscopy, will strongly constrain when a galaxy was stripped, how rapidly it was stripped, and the strength of any starburst at the time of stripping. The UV light changes dramatically over timescales of 0-500 Myr, which are the same timescales over which ICM-ISM interactions take place, making it possible to constrain the most recent effects of the cluster environment on galaxy evolution and if these effects can effectively drive the transformation of spirals into S0s. The deep imaging we propose will enable us to detect age gradients in the stellar populations of the outer disks, which will tell us how rapidly the galaxies are stripped. The cluster locations of recently stripped galaxies and the timescales over which the galaxies are stripped will allow us to constrain the relative importance of stripping that occurs during cluster core passages and stripping which occurs when galaxies encounter an ICM shock outside the core. Ten of these galaxies have already been imaged with GALEX, and we are requesting deep observations of these galaxies, in addition to time to image the remaining eight to the same depth.
Lyman limit systems (LLSs), including MgII absorbers, subdamped and damped Ly-alpha absorbers (DLAs), are uniquely valuable probes of galaxy haloes and the IGM. Recent investigations of transverse correlations on up to 5 Mpc scales between quasars and subDLAs/DLAs for z>2 have constrained quasar-absorber correlation lengths to r~9 Mpc, the absorber HI number density distribution and either bias or quasar variability timescales. We propose a spectroscopic survey toward two large quasar groups (LQGs) at z~0.8 and 1.3 which offer an unprecedented number of bright z<2 quasars, optimal for simultaneous probes of many sight lines. We expect 30-40 LLSs toward ~50 quasars which are UV-bright or indicate a Lyman break. Results will allow us to test the z~1 LLS-quasar correlation on r0 (5-12) comoving Mpc scale with a similar sample size to the z>2 study, to measure the change of correlation with time and compare with structure formation models. The field also has ~500 LBGs at 0.5<z<1.4, which enables a z~1 comparison of the LBG-subDLA relation found at z~2-3 to measure halo evolution, also a constraint on hierarchical models. Finally, we also could confirm a factor 3 overdensity in the LLSs in the LQGs, providing a direct measure of the HI gas content in these likely highly biased structures which are easily visible to z~2-3.
Strong variations in the ratio of H-alpha line flux to FUV flux density strongly imply that the upper end of the Initial Mass Function is not constant. This has major implications for astrophysics ranging from how we measure star formation rates and population ages to understanding the chemical evolution of the universe. This proposal will use the very rich GALEX archive to triple our sample of HI selected galaxies with both H-alpha and UV fluxes, allowing better statistical constraints on the variability of the IMF, while radial profiles of the deeper datasets will extend the dynamic range of the parameter space probed.
FUV/NUV imaging of eight nearby Abell clusters is proposed. All clusters have been observed in Halpha using the KPNO MOSAIC camera on the 0.9m telescope, giving a field of view of 1 degree square, which makes our optical cluster data a perfect match for the GALEX observations. The Halpha images detect star formation in several hundred to 600 galaxies down to ~0.01 Msolar/yr. By comparing the GALEX, Halpha and optical continuum images, we will measure reddening-corrected, spatially resolved star formation rates in a wide range of cluster member galaxies. We will determine how star formation rates and their recent history depend on cluster properties, and on environment, as measured by clustercentric distance, local galaxy surface density, or velocity substructure. We will also determine the incompleteness in surveys of star-forming galaxies.
We propose to perform a Snap survey of high Galactic latitude symbiotic stars. The requested grism observations will allow us to determine whether these symbiotics are powered by accretion or nuclear burning. Our results will have implications for whether symbiotic stars can produce a significant fraction of type Ia supernova, and for understanding the production of jets in these systems. Because this work requires FUV spectra, GALEX is the only observatory that can carry out this project.
We propose to obtain deep GALEX images of the isolated galaxies CIG96 and CIG812. These galaxies are part of the AMIGA project (Analysis of the Interstellar Medium of Isolated Galaxies) and constitute the first two well-defined isolated galaxies where extended-UV emission has been identified. The images here requested will allow us (1) to confirm the nature of these objects are extended-UV-disk galaxies, (2) to study the star formation threshold and law in combination with already-obtained VLA HI maps, and (3) to investigate the role of internal processes in the triggering of the star formation in extended-UV disks.
We propose to measure the cosmic history of star formation in one of the largest fields in the sky with extensive far-IR observations. By combining GALEX images with our IR data we will account for the extinction effects of dust. The SFR histories derived directly from FUV continuum and indirectly from the bolometric FIR dust emission both show strong cosmic evolution. However, the evolution of obscured star formation appears to be more rapid. To understand how dust effects the SF evolution, we will analyze the bi-variate UV/IR properties of two to three thousand galaxies detected at 90um in the ADF-S, including a large sample with z>1. The complete set of thousands of multiwavelength SEDs (including UV, optical, near-IR mid-IR, and far-IR, submm and radio), with reasonably accurate photometric redshifts and a subsample of spectroscopic redshifts, will be valuable for many investigations, such as the role and evolution of extinction in different environments, and the evolution of obscured and unobscured AGN.
Two central components of current studies in galaxy evolution involve (1) unraveling the drivers of star formation at a time when the universe was near its peak production of stars and the causes for the decline of that activity to the present day, and (2) the robust calibration of multiple star formation indicators over the span of cosmic history. Here we propose GALEX archival research that will provide unique new insights into each of these issues. To facilitate this study we will first derive deblended GALEX photometry for all deep GALEX fields (e.g, COSMOS, EGS, SXDS, CDF-S) and make the resulting catalogs, along with ample documentation, publicly available. Next we will investigate calibrations and systematics of UV as a SF indicator by comparing it with our new Halpha observations at z=0.81. Finally, we will characterize UV-based star formation properties in both actively star forming galaxies and those entering a quiescent phase (SF shutdown) at 0.4<z<1.4, and to constrain the rate and explore the role of AGN in the transition of galaxies from star-forming to quiescent.
The Sloan Digital Sky Survey (SDSS) has produced an unprecedented sample of QSOs from 0$<$z$<$6 many of which have been detected in the ultraviolet. We propose an unprecedented survey of 130 high luminosity QSOs in the redshift range 0.9<z<1.22 selected from the GALEX-SDSS surveys. This sample contains the brightest QSOs at z$\sim$1 making it ideal for follow-up studies at all wavelengths. We will use it to 1) Produce the first large spectroscopic sample of QSOs in the rest-frame far-UV in a ``sweet-spot'' redshift range which optimally balances luminosity evolution vs. IGM absorption resulting in the cleanest possible measurements of the Lyman alpha emission lines. 2) Study the poorly understood physics of the Broad-Line Emission Region (BELR) and distinguish between orbital- and outflow-dominated kinematics for the Lyman-alpha line. 3) Advance next generation studies of high redshift re-ionization history by providing crucial information about the shape of emission lines coming from the most luminous QSOs. 4) Establish the best possible QSO sample for follow-up with HST/COS for the study of the intermediate redshift IGM. 5) Investigate the statistics of DLA/LLS and MgII/metal absorbers at a redshift where these systems may be experiencing significant evolution. In this proposal we focus on the first two goals above, but the resulting sample has a broad range of applications.