HUBBLE
SPACE TELESCOPE - Continuing to Collect World Class Science
DAILY
REPORT #5087
PERIOD
COVERED: 5am April 30 - 5am May 03, 2010 (DOY 120/09:00z-123/09:00z)
OBSERVATIONS
SCHEDULED
WFC3/UV/IR
12021
An
Irradiated Disk in an Ultraluminous X-Ray Source
Whether
ultraluminous X-ray sources (ULXs) contain stellar-mass or
intermediate-mass
black holes (IMBHs) is an important, but as yet
unresolved,
astrophysical question. We have discovered variable optical
emission
from the ULX NGC 5408 X-1 that we interpret as reprocessed
emission
in an irradiated disk. We propose simultaneous observations
with
Chandra and HST to test this interpretation and place constraints
on
the geometry of the accretion disk. The observations should provide a
means
to discriminate between stellar-mass versus intermediate-mass
black
holes.
ACS/WFC
11995
CCD
Daily Monitor (Part 2)
This
program comprises basic tests for measuring the read noise and dark
current
of the ACS WFC and for tracking the growth of hot pixels. The
recorded
frames are used to create bias and dark reference images for
science
data reduction and calibration. This program will be executed
four
days per week (Mon, Wed, Fri, Sun) for the duration of Cycle 17. To
facilitate
scheduling, this program is split into three proposals. This
proposal
covers 320 orbits (20 weeks) from 1 February 2010 to 20 June
2010.
WFC3/IR/S/C
11929
IR
Dark Current Monitor
Analyses
of ground test data showed that dark current signals are more
reliably
removed from science data using darks taken with the same
exposure
sequences as the science data, than with a single dark current
image
scaled by desired exposure time. Therefore, dark current images
must
be collected using all sample sequences that will be used in
science
observations. These observations will be used to monitor changes
in
the dark current of the WFC3-IR channel on a day-to-day basis, and to
build
calibration dark current ramps for each of the sample sequences to
be
used by Gos in Cycle 17. For each sample sequence/array size
combination,
a median ramp will be created and delivered to the
calibration
database system (CDBS).
WFC3/UVIS/IR
11909
UVIS
Hot Pixel Anneal
The
on-orbit radiation environment of WFC3 will continually generate new
hot
pixels. This proposal performs the procedure required for repairing
those
hot pixels in the UVIS CCDs. During an anneal, the two-stage
thermo-electric
cooler (TEC) is turned off and the four-stage TEC is
used
as a heater to bring the UVIS CCDs up to ~20 deg. C. As a result of
the
CCD warmup, a majority of the hot pixels will be fixed; previous
instruments
such as WFPC2 and ACS have seen repair rates of about 80%.
Internal
UVIS exposures are taken before and after each anneal, to allow
an
assessment of the procedure's effectiveness in WFC3, provide a check
of
bias, global dark current, and hot pixel levels, as well as support
hysteresis
(bowtie) monitoring and CDBS reference file generation. One
IR
dark is taken after each anneal, to provide a check of the IR
detector.
WFC3/UVIS
11908
Cycle
17: UVIS Bowtie Monitor
Ground
testing revealed an intermittent hysteresis type effect in the
UVIS
detector (both CCDs) at the level of ~1%, lasting hours to days.
Initially
found via an unexpected bowtie-shaped feature in flatfield
ratios,
subsequent lab tests on similar e2v devices have since shown
that
it is also present as simply an overall offset across the entire
CCD,
i.e., a QE offset without any discernable pattern. These lab tests
have
further revealed that overexposing the detector to count levels
several
times full well fills the traps and effectively neutralizes the
bowtie.
Each visit in this proposal acquires a set of three 3x3 binned
internal
flatfields: the first unsaturated image will be used to detect
any
bowtie, the second, highly exposed image will neutralize the bowtie
if
it is present, and the final image will allow for verification that
the
bowtie is gone.
WFC3/UVIS
11905
WFC3
UVIS CCD Daily Monitor
The
behavior of the WFC3 UVIS CCD will be monitored daily with a set of
full-frame,
four-amp bias and dark frames. A smaller set of 2Kx4K
subarray
biases are acquired at less frequent intervals throughout the
cycle
to support subarray science observations. The internals from this
proposal,
along with those from the anneal procedure (Proposal 11909),
will
be used to generate the necessary superbias and superdark reference
files
for the calibration pipeline (CDBS).
COS/FUV
11897
FUV
Spectroscopic Sensitivity Monitoring
The
purpose of this proposal is to monitor sensitivity in each FUV
grating
mode to detect any changes due to contamination or other causes.
COS/NUV
11896
NUV
Spectroscopic Sensitivity Monitoring
The
purpose of this proposal is to monitor sensitivity of each NUV
grating
mode to detect any changes due to contamination or other causes.
WFC3/ACS/UVIS
11877
HST
Cycle 17 and Post-SM4 Optical Monitor
This
program is the Cycle 17 implementation of the HST Optical
Monitoring
Program.
The
36 orbits comprising this proposal will utilize ACS (Wide Field
Channel)
and WFC3 (UVIS Channel) to observe stellar cluster members in
parallel
with multiple exposures over an orbit. Phase retrieval
performed
on the PSF in each image will be used to measure primarily
focus,
with the ability to explore apparent coma, and astigmatism
changes
in WFC3.
The
goals of this program are to: 1) monitor the overall OTA focal
length
for the purposes of maintaining focus within science tolerances
2)
gain experience with the relative effectiveness of phase retrieval on
WFC3/UVIS
PSFs 3) determine focus offset between the imagers and
identify
any SI-specific focus behavior and dependencies
If
need is determined, future visits will be modified to interleave
WFC3/IR
channel and STIS/CCD focii measurements.
FGS
11875
Monitoring
FGS2R2 Distortion and Alignment After SMOV4
This
proposal monitors changes in the FGS2R2 distortion and alignment
after
SMOV4 by observing selected stars in M35 in Position mode. Data
from
each epoch are compared to track changes in FGS2R2. When the rate
of
change becomes sufficiently slow, FGS2R2 will be cleared for a
mini-OFAD
and FGS-FGS alignment calibration (carried out in another
phase
2 proposal).
STIS/CC
11847
CCD
Bias Monitor-Part 2
Monitor
the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1,
and
1x1 at gain = 4, to build up high-S/N superbiases and track the
evolution
of hot columns.
STIS/CC
11845
CCD
Dark Monitor Part 2
Monitor
the darks for the STIS CCD.
FGS
11789
An
Astrometric Calibration of Population II Distance Indicators
In
2002, HST produced a highly precise parallax for RR Lyrae. That
measurement
resulted in an absolute magnitude, M(V)= 0.61+/-0.11, a
useful
result, judged by the over ten refereed citations each year
since.
It is, however, unsatisfactory to have the direct,
parallax-based,
distance scale of Population II variables based on a
single
star. We propose, therefore, to obtain the parallaxes of four
additional
RR Lyrae stars and two Population II Cepheids, or W Vir
stars.
The Population II Cepheids lie with the RR Lyrae stars on a
common
K-band Period-Luminosity relation. Using these parallaxes to
inform
that relationship, we anticipate a zero point error of 0.04
magnitude.
This result should greatly strengthen confidence in the
Population
II distance scale and increase our understanding of RR Lyrae
star
and Pop. II Cepheid astrophysics.
STIS/CCD/MA1
11737
The
Distance Dependence of the Interstellar N/O Abundance Ratio: A Gould
Belt
Influence?
The
degree of elemental abundance homogeneity in the interstellar medium
is
a function of the enrichment and mixing processes that govern
galactic
chemical evolution. Observations of young stars and the
interstellar
gas within ~500 pc of the Sun have revealed a local ISM
that
is so well-mixed it is having an impact on ideas regarding the
formation
of extrasolar planets. However, the situation just beyond the
local
ISM is not so clear. Sensitive UV absorption line measurements
have
recently revealed a pattern of inhomogeneities in the interstellar
O,
N, and Kr gas-phase abundances at distances of ~500 pc and beyond
that
appear nucleosynthetic in origin rather than due to dust depletion.
In
particular, based on a sample of 13 sightlines, Knauth et al. (2006)
have
found that the nearby stars (d < 500 pc) exhibit a mean
interstellar
N/O abundance ratio that is significantly higher (0.18 dex)
than
that toward the more distant stars. Interestingly, all of their
sightlines
lie in the sky vicinity of the Gould Belt of OB associations,
molecular
clouds, and diffuse gas encircling the Sun at a distance of
~400
pc. Is it possible that mixing processes have not yet smoothed out
the
recent ISM enrichment by massive stars in the young Belt region? By
measuring
the interstellar N/O ratios in a strategic new sample of
sightlines
with STIS, we propose to test the apparent N/O homogeneity
inside
the Gould Belt and determine if the apparent decline in the N/O
ratio
with distance is robust and associated with the Belt region.
WFC3/UV/IR
11709
Stretching
the Diversity of Cosmic Explosions: The Supernovae of
Gamma-ray
Bursts
While
the association between gamma-ray bursts (GRBs) and massive stars
is
robust, there is a large diversity of properties among supernovae
(SNe)
associated with GRBs. The converse is also true: Several recent
events
show that there is a large brightness range among high energy
transients
associated with SNe. As part of a comprehensive program, we
propose
to use HST in order to search for and characterize the SNe
associated
with GRB.
HST
offers the means to cleanly separate the light curve of the GRB
afterglow
from the supernova, and to remove the contamination from the
host
galaxy, opening a clear path to the fundamental parameters of the
SN,
and thence to the progenitor. From these observations, we will
determine
the absolute magnitude at maximum, the shape of the spectral
energy
distribution, and any change over time of the energy
distribution.
We will also measure the rate of decay of the exponential
tail.
Merged
with the ground-based data that we will obtain for each event, we
will
be able to compare our data set to models and constrain the energy
of
the explosion, the mass of the ejecta and the mass of Nickel
synthesized
during the explosion. These results will shed light on the
apparent
variety of supernovae associated with gamma-ray bursts and
X-ray
flashes, and on the relation between these SNe and other, more
common,
types of core-collapse explosions.
COS/FUV
11687
SNAPing
Coronal Iron
This
is a Snapshot Survey to explore two forbidden lines of highly
ionized
iron in late-type coronal sources. Fe XII 1349 (T~ 2 MK) and Fe
XXI
1354 (T~ 10 MK) -- well known to Solar Physics -- have been detected
in
about a dozen cool stars, mainly with HST/STIS. The UV coronal
forbidden
lines are important because they can be observed with velocity
resolution
of better than 15 km/s, whereas even the state-of-the-art
X-ray
spectrometers on Chandra can manage only 300 km/s in the kilovolt
band
where lines of highly ionized iron more commonly are found. The
kinematic
properties of hot coronal plasmas, which are of great interest
to
theorists and modelers, thus only are accessible in the UV at
present.
The bad news is that the UV coronal forbidden lines are faint,
and
were captured only in very deep observations with STIS. The good
news
is that 3rd-generation Cosmic Origins Spectrograph, slated for
installation
in HST by SM4, in a mere 25 minute exposure with its G130M
mode
can duplicate the sensitivity of a landmark 25-orbit STIS E140M
observation
of AD Leo, easily the deepest such exposure of a late-type
star
so far. Our goal is to build up understanding of the properties of
Fe
XII and Fe XXI in additional objects beyond the current limited
sample:
how the lineshapes depend on activity, whether large scale
velocity
shifts can be detected, and whether the dynamical content of
the
lines can be inverted to map the spatial morphology of the stellar
corona
(as in "Doppler Imaging''). In other words, we want to bring to
bear
in the coronal venue all the powerful tricks of spectroscopic
remote
sensing, well in advance of the time that this will be possible
exploiting
the corona's native X-ray radiation. The 1290-1430 band
captured
by side A of G130M also contains a wide range of key plasma
diagnostics
that form at temperatures from below 10, 000 K (neutral
lines
of CNO), to above 200, 000 K (semi-permitted O V 1371), including
the
important bright multiplets of C II at 1335 and Si IV at 1400;
yielding
a diagnostic gold mine for the subcoronal atmosphere. Because
of
the broad value of the SNAP spectra, beyond the coronal iron project,
we
waive the normal proprietary rights.
WFC3/UVIS
11675
Stellar
Forensics: A Post-Explosion View of the Progenitors of
Core-Collapse
Supernovae
Recent
studies have used high spatial resolution HST observations of SN
sites
to identify the progenitors of core-collapse SNe on pre-explosion
images.
These studies have set constraints about the nature of massive
stars
and their evolution just prior to their explosion as SNe. Now, at
late-times
when the SNe have faded sufficiently, it is possible to
return
to the sites of these core-collapse SNe to search for clues about
the
nature of their progenitors. We request time to conduct deep,
late-time,
high-resolution imaging with ACS/HRC of the sites of six
core-collapse
SNe. In this program we aim to: 1) confirm our
identifications,
that were made with HST pre- explosion images, of the
red
supergiant progenitors of four Type IIP SNe (1999ev, 2003gd, 2004A
and
2005cs), by observing if the objects identified as the progenitors
are
now missing; 2) place precise constraints on the progenitor of the
Type
Ic SN 2007gr by studying its host cluster; and 3) confirm our
identification
of an LBV-like outburst of an unstable WR star as
belonging
to the progenitor of a Type Ib-n core-collapse SN (2006jc),
using
broad and narrow- band imaging to search for emission line stars
in
its locality. The deep imaging will also allow to probe the stellar
populations
in the immediate vicinities of these SNe, that were
previously
obscured by the progenitors and the bright SNe. HST provides
the
unique combination of high- resolution optical imaging at very faint
magnitudes
that will facilitate this study.
WFC3/UV/IR
11664
The
WFC3 Galactic Bulge Treasury Program: Populations, Formation
History,
and Planets
Exploiting
the full power of the Wide Field Camera 3 (WFC3), we propose
deep
panchromatic imaging of four fields in the Galactic bulge. These
data
will enable a sensitive dissection of its stellar populations,
using
a new set of reddening-free photometric indices we have
constructed
from broad-band filters across UV, optical, and near-IR
wavelengths.
These indices will provide accurate temperatures and
metallicities
for hundreds of thousands of individual bulge stars.
Proper
motions of these stars derived from multi-epoch observations will
allow
separation of pure bulge samples from foreground disk
contamination.
Our catalogs of proper motions and panchromatic
photometry
will support a wide range of bulge studies.
Using
these photometric and astrometric tools, we will reconstruct the
detailed
star-formation history as a function of position within the
bulge,
and thus differentiate between rapid- and extended-formation
scenarios.
We will also measure the dependence of the stellar mass
function
on metallicity, revealing how the characteristic mass of star
formation
varies with chemistry. Our sample of bulge stars with accurate
metallicities
will include 12 candidate hosts of extrasolar planets.
Planet
frequency is correlated with metallicity in the solar
neighborhood;
our measurements will extend this knowledge to a remote
environment
with a very distinct chemistry.
Our
proposal also includes observations of six well-studied globular and
open
star clusters; these observations will serve to calibrate our
photometric
indices, provide empirical population templates, and
transform
the theoretical isochrone libraries into the WFC3 filter
system.
Besides enabling our own program, these products will provide
powerful
new tools for a host of other stellar-population investigations
with
HST/WFC3. We will deliver all of the products from this Treasury
Program
to the community in a timely fashion.
WFC3/UV/ACS/WFC
11636
First
Resolved Imaging of Escaping Lyman Continuum
The
emission from star-forming galaxies appears to be responsible for
reionization
of the universe at z > 6. However, the models that attempt
to
describe the detailed impact of high-redshift galaxies on the
surrounding
inter-galactic medium (IGM) are strongly dependent upon
several
uncertain parameters. Perhaps the most uncertain is the fraction
of
HI-ionizing photons produced by young stars that escape into the IGM.
Most
attempts to measure this "escape fraction" have produced null
results.
Recently, a small subset of z~3 Lyman Break Galaxies (LBGs) has
been
found exhibiting large escape fractions. It remains unclear
however,
what differentiates them from other LBGs. Several models
attempt
to explain how such a large fraction of ionizing continuum can
escape
through the HI and dust in the ISM (eg. "chimneys" created by SNe
winds,
globular cluster formation, etc.), each producing unique
signatures
which can be observed with resolved imaging of the escaping
Lyman
continuum. To date, there are only six LBGs with individual
detections
of escaping Lyman continuum at any redshift. We propose a
single
deep, high resolution WFC3/UVIS image of the ionizing continuum
(F336W)
and the rest-frame UV/optical (F606W/F814W/F160W) of five of
these
six LBGs with large escape fractions. These LBGs have a high
surface
density and large escape fractions, and lie at the optimal
redshift
for Lyman continuum imaging with UVIS filters, making our
sample
especially suitable for follow-up. With these data we will
discern
the mechanisms responsible for producing large escape fractions,
and
therefore gain insight into the process of reionization.
WFC3/UVIS
11628
Globular
Cluster Candidates for Hosting a Central Black Hole
We
are continuing our study of the dynamical properties of globular
clusters
and we propose to obtain surface brightness profiles for high
concentration
clusters. Our results to date show that the distribution
of
central surface brightness slopes do not conform to standard models.
This
has important implications for how they form and evolve, and
suggest
the possible presence of central intermediate-mass black holes.
From
our previous archival proposals (AR-9542 and AR- 10315), we find
that
many high concentration globular clusters do not have flat cores or
steep
central cusps, instead they show weak cusps. Numerical simulations
suggest
that clusters with weak cusps may harbor intermediate-mass black
holes
and we have one confirmation of this connection with omega
Centauri.
This cluster shows a shallow cusp in its surface brightness
profile,
while kinematical measurements suggest the presence of a black
hole
in its center. Our goal is to extend these studies to a sample
containing
85% of the Galactic globular clusters with concentrations
higher
than 1.7 and look for objects departing from isothermal behavior.
The
ACS globular cluster survey (GO-10775) provides enough objects to
have
an excellent coverage of a wide range of galactic clusters, but it
contains
only a couple of the ones with high concentration. The proposed
sample
consists of clusters whose light profile can only be adequately
measured
from space-based imaging. This would take us close to
completeness
for the high concentration cases and therefore provide a
more
complete list of candidates for containing a central black hole.
The
dataset will also be combined with our existing kinematic
measurements
and enhanced with future kinematic studies to perform
detailed
dynamical modeling.
STIS/CCD
11606
Dynamical
Hypermassive Black Hole Masses
We
will use STIS spectra to derive the masses of 5 hypermassive black
holes
(HMBHs). From the observed scaling relations defined by less
massive
spheroids, these objects are expected to reside at the nuclei of
host
galaxies with stellar velocity dispersions greater than 320 km/s.
These
5 targets have confirmed regular gas distributions on the scales
of
the black hole sphere of influence. It is essential that the sphere
of
influence is resolved for accurate determinations of black hole mass
(0.1").
These scales cannot be effectively observed from the ground.
Only
two HMBHs have had their masses modeled so far; it is impossible to
draw
any general conclusions about the connections between HMBH mass and
their
massive host galaxies. With these 5 targets we will determine
whether
these HMBHs deviate from the scaling relations defined by less
massive
spheroids. A larger sample will allow us to firmly anchor the
high
mass end of the correlation between black hole mass and stellar
velocity
dispersion, and other scaling relations. Therefore we are also
conducting
a SNAPshot program with which we expect to detect a further
24
HMBH candidates for STIS observation in future cycles. At the
completion
of this project we will have populated the high mass end of
the
scaling relations with the sample sizes enjoyed by less massive
spheroids.
ACS/WFC3
11604
The
Nuclear Structure of OH Megamaser Galaxies
We
propose a snapshot survey of a complete sample of 80 OH megamaser
galaxies.
Each galaxy will be imaged with the ACS/WFC through F814W and
a
linear ramp filter (FR656N or FR716N or FR782N or FR853N) allowing us
to
study both the spheroid and the gas morphology in Halpha + [N II]. We
will
use the 9% ramps FR647M (5370-7570 angstroms) centered at 7000
angstroms
and FR914M (7570-10, 719 angstroms) 8000 angstroms for
continuum
subtraction for the high and low z objects respectively. OH
megamaser
galaxies (OHMG) form an important class of ultraluminous
IR-galaxies
(ULIRGs) whose maser lines emit QSO-like luminosities.
ULIRGs
in general are associated with recent mergers but it is often
unclear
whether their power output is dominated by starbursts or a
hidden
QSO because of the high absorbing columns which hide their nuclei
even
at X-ray wavelengths. In contrast, OHMG exhibit strong evidence for
the
presence of an energetically important and recently triggered active
nucleus.
In particular it is clear that much of the gas must have
already
collapsed to form a nuclear disk which may be the progenitor of
a
circum-nuclear torus, a key element of the unified scheme of AGN. A
great
advantage of studying OHMG systems over the general ULIRG
population,
is that the circum-nuclear disks are effectively "fixed" at
an
inner, edge on, orientation, eliminating varying inclination as a
nuisance
parameter. We will use the HST observations in conjunction with
existing
maser and spectroscopic data to construct a detailed picture of
the
circum-nuclear regions of a hitherto relatively neglected class of
galaxy
that may hold the key to understanding the relationship between
galaxy
mergers, nuclear star-formation, and the growth of massive black
holes
and the triggering of nuclear activity.
ACS/WFC3
11599
Distances
of Planetary Nebulae from SNAPshots of Resolved Companions
Reliable
distances to individual planetary nebulae (PNe) in the Milky
Way
are needed to advance our understanding of their spatial
distribution,
birthrates, influence on galactic chemistry, and the
luminosities
and evolutionary states of their central stars (CSPN). Few
PNe
have good distances, however. One of the best ways to remedy this
problem
is to find resolved physical companions to the CSPN and measure
their
distances by photometric main-sequence fitting. We have previously
used
HST to identify and measure probable companions to 10 CSPN, based
on
angular separations and statistical arguments only. We now propose to
use
HST to re-observe 48 PNe from that program for which additional
companions
are possibly present. We then can use the added criterion of
common
proper motion to confirm our original candidate companions and
identify
new ones in cases that could not confidently be studied before.
We
will image the region around each CSPN in the V and I bands, and in
some
cases in the B band. Field stars that appear close to the CSPN by
chance
will be revealed by their relative proper motion during the 13+
years
since our original survey, leaving only genuine physical
companions
in our improved and enlarged sample. This study will increase
the
number of Galactic PNe with reliable distances by 50 percent and
improve
the distances to PNe with previously known companions.
WFC3/UVIS
11594
A
WFC3 Grism Survey for Lyman Limit Absorption at z=2
We
propose to conduct a spectroscopic survey of Lyman limit absorbers at
redshifts
1.8 < z < 2.5, using WFC3 and the G280 grism. This proposal
intends
to complete an approved Cycle 15 SNAP program (10878), which was
cut
short due to the ACS failure. We have selected 64 quasars at 2.3 < z
<
2.6 from the Sloan Digital Sky Survey Spectroscopic Quasar Sample, for
which
no BAL signature is found at the QSO redshift and no strong metal
absorption
lines are present at z > 2.3 along the lines of sight. The
survey
has three main observational goals. First, we will determine the
redshift
frequency dn/dz of the LLS over the column density range 16.0 <
log(NHI)
< 20.3 cm^-2. Second, we will measure the column density
frequency
distribution f(N) for the partial Lyman limit systems (PLLS)
over
the column density range 16.0 < log(NHI) < 17.5 cm^-2. Third, we
will
identify those sightlines which could provide a measurement of the
primordial
D/H ratio. By carrying out this survey, we can also help
place
meaningful constraints on two key quantities of cosmological
relevance.
First, we will estimate the amount of metals in the LLS using
the
f(N), and ground based observations of metal line transitions.
Second,
by determining f(N) of the PLLS, we can constrain the amplitude
of
the ionizing UV background at z~2 to a greater precision. This survey
is
ideal for a snapshot observing program, because the on-object
integration
times are all well below 30 minutes, and follow-up
observations
from the ground require minimal telescope time due to the
QSO
sample being bright.
ACS/WFC/WFC3/UV
11578
The
Extremely Metal-Poor BCD Galaxy DDO 68: a Young Galaxy in the Local
Universe
?
A
long standing question in astrophysics is the existence of young
galaxies,
in which stars are now forming for the first time, in the
nearby
(i.e., present-day) universe. Such galaxies would be the local
analogs
of primordial galaxies observed at high redshift. The most
promising
candidates have long been the most metal-poor systems,
including
dwarf irregulars (dIrrs) and blue compact dwarfs (BCDs).
However,
in many dIrrs and BCDs studied with HST an old (1 Gyr)
underlying
stellar population, as traced by red giant branch (RGB)
stars,
has been unambiguously detected. Even in I Zw 18, which is the
most-metal
poor prototype of the class and long the most controversial
case,
our group has recently succeeded in detecting an RGB. Nonetheless,
there
remains the possibility that the star formation histories of
BCDs/dIrrs
vary from galaxy to galaxy, and that truly young galaxies do
exist
in the local universe. A new test of these issues has only
recently
become possible with the identification of DDO 68 as an
extremely
metal-poor galaxy with an oxygen abundance equal to that of I
Zw
18 (12+(O/H)=7.21). This galaxy is about a factor of 2-3 closer than
I
Zw 18, which yields the opportunity to avoid the many ambiguities that
have
plagued studies of I Zw 18. Also, DDO 68 resides in a void, making
it
more likely that star formation has been suppressed for a very long
time.
We will observe DDO 68 with ACS/WFC in F606W and F814W, plus F658N
(Halpha)
to correct the broad F606W for gas contamination. We will use
WFC3
in parallel with the same filters to study radial population
gradients.
Deep color-magnitude diagrams (CMDs) reaching the depth of
one
magnitude below the predicted RGB tip will be constructed and
interpreted
based on synthetic CMD fitting. These data will determine
unambiguously
whether DDO 68 has an underlying old (RGB) stellar
population
or is forming stars for the first time. Finding just a single
nearby
``young'' galaxy would have profound cosmological implications.
STIS/CCD
11567
Boron
Abundances in Rapidly Rotating Early-B Stars
Models
of rotation in early-B stars predict that rotationally driven
mixing
should deplete surface boron abundances during the main-sequence
lifetime
of many stars. However, recent work has shown that many boron
depleted
stars are intrinsically slow rotators for which models predict
no
depletion should have occurred, while observations of nitrogen in
some
more rapidly rotating stars show less mixing than the models
predict.
Boron can provide unique information on the earliest stages of
mixing
in B stars, but previous surveys have been biased towards narrow-
lined
stars because of the difficulty in measuring boron abundances in
rapidly
rotating stars. The two targets observed as part of our Cycle 13
SNAP
program 10175, just before STIS failed, demonstrate that it is
possible
to make useful boron abundance measurements for early-B stars
with
Vsin(i) above 100 km/s. We propose to extend that survey to a large
enough
sample of stars to allow statistically significant tests of
models
of rotational mixing in early-B stars.
NIC2/WFC3/IR
11548
Infrared
Imaging of Protostars in the Orion A Cloud: The Role of
Environment
in Star Formation
We
propose NICMOS and WFC3/IR observations of a sample of 252 protostars
identified
in the Orion A cloud with the Spitzer Space Telescope. These
observations
will image the scattered light escaping the protostellar
envelopes,
providing information on the shapes of outflow cavities, the
inclinations
of the protostars, and the overall morphologies of the
envelopes.
In addition, we ask for Spitzer time to obtain 55-95 micron
spectra
of 75 of the protostars. Combining these new data with existing
3.6
to 70 micron photometry and forthcoming 5-40 micron spectra measured
with
the Spitzer Space Telescope, we will determine the physical
properties
of the protostars such as envelope density, luminosity,
infall
rate, and outflow cavity opening angle. By examining how these
properties
vary with stellar density (i.e. clusters vs. groups vs.
isolation)
and the properties of the surrounding molecular cloud; we can
directly
measure how the surrounding environment influences protostellar
evolution,
and consequently, the formation of stars and planetary
systems.
Ultimately, this data will guide the development of a theory of
protostellar
evolution.
NIC3/WFC3/IR
11149
Characterizing
the Stellar Populations in Lyman-Alpha Emitters and Lyman
Break
Galaxies at 5.7<z<7 in the Subaru Deep Field
The
epoch of reionization marks a major phase transition of the
Universe,
during which the intergalactic space became transparent to UV
photons.
Determining when this occurred and the physical processes
involved
represents the latest frontier in observational cosmology. Over
the
last few years, searches have intensified to identify the population
of
high-redshift (z>6) galaxies that might be responsible for this
process,
but the progress is hampered partly by the difficulty of
obtaining
physical information (stellar mass, age, star formation
rate/history)
for individual sources. This is because the number of z>6
galaxies
that have both secure spectroscopic redshifts and high-quality
infrared
photometry (especially with Spitzer/IRAC) is still fairly
small.
Considering that only several photometric points are available
per
source, and that many model SEDs are highly degenerate, it is
crucial
to obtain as many observational constraints as possible for each
source
to ensure the validity of SED modeling. To better understand the
physical
properties of high-redshift galaxies, we propose here to
conduct
HST/NICMOS (72 orbits) and Spitzer/IRAC (102 hours) imaging of
spectroscopically
confirmed, bright (z<26 mag (AB)) Ly-alpha emitters
(LAEs)
and Lyman-break galaxies (LBGs) at 5.7<z<7 selected from the
Subaru
Deep Field. Spectroscopic redshifts remove one critical free
parameter
from SED modeling while bright source magnitudes ensure
high-quality
photometric data. By making accurate determinations of
stellar
masses, ages, and star-formation histories, we will specifically
address
the following major questions: (1) Do LAEs and LBGs represent
physically
different galaxy populations at z>6 as suggested recently?
(2)
Is Ly-alpha emission systematically suppressed at z>6 with respect
to
continuum emission? (i.e., are we reaching the epoch of incomplete
reionization?),
and (3) Do we see any sign of abnormally young stellar
population
in any of the z>6 galaxies?
WFC3/ACS/IR
11142
Revealing
the Physical Nature of Infrared Luminous Galaxies at 0.3<z<2.7
Using
HST and Spitzer
We
aim to determine physical properties of IR luminous galaxies at
0.3<z<2.7
by requesting coordinated HST/NIC2 and MIPS 70um observations
of
a unique, 24um flux-limited sample with complete Spitzer mid-IR
spectroscopy.
The 150 sources investigated in this program have S(24um)
>
0.8mJy and their mid-IR spectra have already provided the majority
targets
with spectroscopic redshifts (0.3<z<2.7). The proposed
150~orbits
of NIC2 and 66~hours of MIPS 70um will provide the physical
measurements
of the light distribution at the rest-frame ~8000A and
better
estimates of the bolometric luminosity. Combining these
parameters
together with the rich suite of spectral diagnostics from the
mid-IR
spectra, we will (1) measure how common mergers are among LIRGs
and
ULIRGs at 0.3<z<2.7, and establish if major mergers are the drivers
of
z>1 ULIRGs, as in the local Universe, (2) study the co-evolution of
star
formation and blackhole accretion by investigating the relations
between
the fraction of starburst/AGN measured from mid-IR spectra vs.
HST
morphologies, L(bol) and z, and (3) obtain the current best
estimates
of the far-IR emission, thus L(bol) for this sample, and
establish
if the relative contribution of mid-to-far IR dust emission is
correlated
with morphology (resolved vs. unresolved).
FLIGHT
OPERATIONS SUMMARY:
Significant
Spacecraft Anomalies: (The following are preliminary reports
of
potential non-nominal performance that will be investigated.)
HSTARS:
(None)
COMPLETED
OPS REQUEST: (None)
COMPLETED
OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS
GSAcq
25
25
FGS
REAcq 22
22
OBAD
with Maneuver 22 22
SIGNIFICANT
EVENTS: (None)