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Cycle 6 Information
GALEX Project at Caltech |
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AN ABSTRACT FROM CYCLE 5
Click on the
proposal number for the abstract you would like to view
Proposal #
001: “FINDING UV-VARIABLE AGN"
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.
Proposal #
002: “THE ROLE OF ENVIRONMENT IN THE EVOLUTION OF LOW MASS ALFALFA
GALAXIES"
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.
Proposal #
007: “FOLLOWING THE PULSATIONS OF GW LIB AND V455 AND AFTER
SUPEROUTBURST"
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.
Proposal #
008: “THE FIRST LARGE STATISTICAL STUDY OF THE UV CHARACTER OF BL
LAC OBJECTS"
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.
Proposal #
014: “UV SPECTROSCOPY 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 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,
SNe
Ia
(~10
objects observed), while data for SN of all other types (core-collapse events)
is almost non-existent. To remedy this situation, we have undertaken
target-of-opportunity GALEX spectroscopic observations of nearby, bright,
core-collapse SN in cycles 1-4, and so far observed 4 events. Following the
successful implementation of our program, we request here similar spectroscopic
observations for additional SNe. The accumulated GALEX data on non-Ia events,
combined with the results from past efforts using HST and IUE, is leading
toward a full characterization of the UV spectral evolution of SNe of all
types.
Proposal
# 015: “THE WAVELENGTH DEPENDENCE OF GALACTIC STRUCTURE"
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).
Proposal #
016: “LEGACY OBSERVATIONS OF DISTANT GALAXY CLUSTERS AND
GROUPS"
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.
Proposal #
018: “STAR FORMATION ALONG SUPERCLUSTER FILAMENTS"
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.
Proposal # 021:
“STAR TRAILS: PROBING AGB-ISM INTERACTION VIA MOLECULAR HYDROGEN
FLUORESCENCE"
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.
Proposal #
025: “A LABORATORY FOR GALAXY EVOLUTION: DEEP IMAGING OF THE COMA
CLUSTER CORE"
.\ 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.
Proposal #
026: “THE MASSIVE DWARF NOVA HD 109962"
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.
Proposal #
027: “GALEX IDENTIFICATION OF HUNDREDS OF FAR-UV-BRIGHT QUASARS: A
HIGH YIELD FOR HELIUM IGM STUDIES"
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.
Proposal #
028: “EXTENDED GALEX COVERAGE OF THE CFHT "WIDE" LEGACY
SURVEY"
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.
Proposal #
031: “GALEX IMAGING OF THE COOLING-FLOW CLUSTER ABELL 1795"
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.
Proposal #
034: “A SURVEY OF STAR FORMATION IN ELLIPTICAL GALAXIES"
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
OB
stars. This line can be
detected by GALEX with greater sensitivity than all previous instrument, including HST. As a proof of concept, we
obtained a spectrum of a cooling flow elliptical IC 1459, which shows the CIV
feature. Here we propose to obtain spectra of a dozen ellipticals in a single
field in the Fornax cluster. This representative
sample will define the extent of star formation in normal elliptical galaxies.
Proposal
# 036: “STELLAR POPULATIONS AND LARGE SCALE OUTFLOWS IN GALEX
DISCOVERED LYMAN ALPHA GALAXIES"
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.
Proposal #
038: “UV PROPERTIES OF A COMPLETE SAMPLE OF LUMINOUS INFRARED
GALAXIES IN THE LOCAL UNIVERSE"
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.
Proposal #
039: “THE NATURE OF H-ALPHA DOTS"
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.
Proposal #
040: “A SYSTEMATIC SEARCH FOR NEARBY WHITE DWARFS IN THE GALEX
ARCHIVE: POSITIONS AND MOTIONS OF 100,000 DISK AND
HALO WD."
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.
Proposal #
041: “UV PROPERTIES OF GALAXIES IN THE HDF-S"
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.
Proposal # 042:
“RESONANCES AND DISK REGROWTH IN E/S0 GALAXIES"
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.
Proposal #
044: “A GALEX SEARCH FOR THE MISSING YOUNG LOW-MASS STARS WITHIN
100 PC"
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.
Proposal #
047: “STAR-FORMATION AND AGES OF TYPE IA SUPERNOVA HOST
GALAXIES"
Understanding the progenitors of
Type
Ia
supernovae
is important for assessing the reliability of these "standardized
candles" for measuring the accelerating expansion of the Universe. Recent
measurements at both high and low redshift suggest the possibility of two
progenitor channels - one tightly tied to the host galaxy star formation rate
and having a short delay time, and the other consisting of systems whose
incidence is proportional to the total stellar mass and which explode many Gyr after the progenitor system is originally formed. We
propose to use GALEX UV imaging to measure star formation rates and constrain
ages for the the host galaxies of a large new sample
of nearby Hubble-flow Type Ia supernovae. These host galaxies properties will
be correlated with deviations from the Hubble diagram, as well as the shapes
and evolution of features in the supernova spectra, using a large database of spectrophotometry in order to look for direct signatures of
these two possible progenitor channels.
Proposal #
048: “GALEX-GAMA: UV/OPTICAL/NEAR-IR/FAR-IR/RADIO OBSERVATIONS OF
~100K GALAXIES"
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.
Proposal #
051: “STAR FORMATION IN NGC4532/DDO 137'S TIDAL DWARF GALAXIES AND
500 KPC HI STREAM"
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.
Proposal #
052: “2175 A DUST MAP OF THE MILKY
WAY"
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.
Proposal #
054: “PROBING BINARY COMPANIONS AND ACCRETION DISKS IN AGB"
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.
Proposal #
055: “MAXIMIZING GALEX COVERAGE OF THE KEPLER FIELD"
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.
Proposal #
057: “DEEP UV IMAGING OF STRIPPED SPIRAL GALAXIES IN THE VIRGO
CLUSTER"
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.
Proposal #
059: “LYMAN LIMIT SYSTEMS TOWARD DENSE QUASAR REGIONS AT Z~1"
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.
Proposal #
061: “AN ARCHIVAL EXTENSION OF SUNGG TO PROBE THE IMF"
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.
Proposal #
063: “STAR FORMATION IN AND AROUND NEARBY GALAXY CLUSTERS"
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.
Proposal #
064: “THE POWER AT THE HEART OF SYMBIOTIC SYSTEMS"
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.
Proposal #
065: “DEEP GALEX IMAGING OF THE ISOLATED EXTENDED-UV DISKS OF CIG96
AND CIG812"
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.
Proposal #
067: “MEDIUM AND DEEP IMAGING OF THE AKARI DEEP FIELD SOUTH"
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.
Proposal #
068: “GALEX DEEP SURVEY - CALIBRATION OF STAR FORMATION AND THE
TRANSITIONAL GALAXIES AT Z~0.8"
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.
Proposal #
070: “A SNAPSHOT SPECTROSCOPIC SURVEY OF THE HIGHEST LUMINOSITY
QSOS: WINDS, REIONIZATION AND THE GALEX LEGACY"
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.
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