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