HUBBLE
SPACE TELESCOPE - Continuing to Collect World Class Science
DAILY
REPORT #5040
PERIOD
COVERED: 5am February 24 - 5am February 25, 2010 (DOY 055/10:00z-056/10:00z)
OBSERVATIONS
SCHEDULED
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.
COS/NUV/FUV
11718
The
Stellar Halos of Dwarf Galaxies
The
metal-poor stellar halo is the oldest extended structure in the
Galaxy.
Such halos are thought to form through hierarchical merging, and
contain
stars pulled from accreted subhalos. The diffuse stellar halo
therefore
stores information about the prop reties of the accreted
galaxies
(i.e., their orbits, stellar masses, and metallicities). It is
therefore
unsurprising that stellar halos have become a popular probe of
the
early epoch of galaxy formation.
Almost
all current work on stellar halos has focused on massive
galaxies,
however. We propose to extend the work on stellar halos to
much
lower mass scales, by studying the halos of faint dwarf galaxies.
By
taking halo studies into the dwarf galaxy regime, we can probe
exceptionally
small mass scales for the accreted halos. At these mass
scales
the effects of reionization and supernova feedback have the
largest
impact on the galaxy population. Stellar halos of dwarf galaxies
are
therefore a sensitive probe of the key processes needed to resolve
the
lack of substructure observed at low masses.
We
are requesting two far-field ACS pointings for the three closest
isolated
nearby dwarf irregular galaxies whose inner halos have already
been
mapped with the ACS Nearby Galaxy Survey Treasury. These outer
fields
will allow us to trace the halo out to roughly half the virial
radius,
further than any previous study. We will use the resulting
distribution
of halo stars (1) to unambiguously measure the structure of
the
stellar halo, with minimal contamination from the main galaxy; (2)
to
constrain the flattening of the stellar halo; (3) to measure the
metallicity
of halo stars as a function of radius; (4) to correlate any
changes
in halo profile with changes in metallicity. The resulting data
will
constrain models of halo accretion and the epoch of reionization.
STIS/CCD
11844
CCD
Dark Monitor Part 1
The
purpose of this proposal is to monitor the darks for the STIS CCD.
STIS/CCD
11846
CCD
Bias Monitor-Part 1
The
purpose of this proposal is to 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/MA1/MA2
11857
STIS
Cycle 17 MAMA Dark Monitor
This
proposal monitors the behavior of the dark current in each of the
MAMA
detectors.
The
basic monitor takes two 1380s ACCUM darks each week with each
detector.
However, starting Oct 5, pairs are only included for weeks
that
the LRP has external MAMA observations planned. The weekly pairs of
exposures
for each detector are linked so that they are taken at
opposite
ends of the same SAA free interval. This pairing of exposures
will
make it easier to separate long and short term temporal variability
from
temperature dependent changes.
For
both detectors, additional blocks of exposures are taken once every
six
months. These are groups of five 1314s FUV-MAMA Time-Tag darks or
five
3x315s NUV ACCUM darks distributed over a single SAA-free interval.
This
will give more information on the brightness of the FUV MAMA dark
current
as a function of the amount of time that the HV has been on, and
for
the NUV MAMA will give a better measure of the short term
temperature
dependence.
WFC3/ACS/UVIS/IR
11570
Narrowing
in on the Hubble Constant and Dark Energy
A
measurement of the Hubble constant to a precision of a few percent
would
be a powerful aid to the investigation of the nature of dark
energy
and a potent "end-to end" test of the present cosmological model.
In
Cycle 15 we constructed a new streamlined distance ladder utilizing
high-
quality type Ia supernova data and observations of Cepheids with
HST
in the near-IR to minimize the dominant sources of systematic
uncertainty
in past measurements of the Hubble constant and reduce its
total
uncertainty to a little under 5%. Here we propose to exploit this
new
route to reduce the remaining uncertainty by more than 30%,
translating
into an equal reduction in the uncertainty of the equation
of
state of dark energy. We propose three sets of observations to reach
this
goal: a mosaic of NGC 4258 with WFC3 in F160W to triple its sample
of
long period Cepheids, WFC3/F160W observations of the 6 ideal SN Ia
hosts
to triple their samples of Cepheids, and observations of NGC 5584
the
host of a new SN Ia, SN 2007af, to discover and measure its Cepheids
and
begin expanding the small set of SN Ia luminosity calibrations.
These
observations would provide the bulk of a coordinated program aimed
at
making the measurement of the Hubble constant one of the leading
constraints
on dark energy.
WFC3/IR
11189
Probing
the Early Universe with GRBs
Cosmology
is beginning to constrain the nature of the earliest stars and
galaxies
to form in the Universe, but direct observation of galaxies at
z>6
remains highly challenging due to their scarcity, intrinsically
small
size, and high luminosity distance. GRB afterglows, thanks to
their
extreme luminosities, offer the possibility of circumventing these
normal
constraints by providing redshifts and spectral information which
couldn't
be obtained through direct observation of the host galaxies
themselves.
In addition, the association of GRBs with massive stars
means
that they are an indicator of star formation, and that their hosts
are
likely responsible for a large proportion of the ionizing radiation
during
that era. Our collaboration is conducting a campaign to rapidly
identify
and study candidate very high redshift bursts, bringing to bear
a
network of 2, 4 and 8m telescopes with near-IR instrumentation. Swift
has
proven capable of detecting faint, distant GRBs, and reporting
accurate
positions for many bursts in near real-time. Here we propose to
continue
our HST program of targeting GRBs at z~6 and above. HST is
crucial
to this endeavor, allowing us (a) to characterize the basic
properties,
such as luminosity and color, and in some cases
morphologies,
of the hosts, which is essential to understanding these
primordial
galaxies and their relationship to other galaxy populations;
and
(b) to monitor the late time afterglows and hence compare them to
lower-z
bursts and test the use of GRBs as standard candles.
WFC3/IR
11719
A
Calibration Database for Stellar Models of Asymptotic Giant Branch
Stars
Studies
of galaxy formation and evolution rely increasingly on the
interpretation
and modeling of near-infrared observations. At these
wavelengths,
the brightest stars are intermediate mass asymptotic giant
branch
(AGB) stars. These stars can contribute nearly 50% of the
integrated
luminosity at near infrared and even optical wavelengths,
particularly
for the younger stellar populations characteristic of
high-redshift
galaxies (z>1). AGB stars are also significant sources of
dust
and heavy elements. Accurate modeling of AGB stars is therefore of
the
utmost importance.
The
primary limitation facing current models is the lack of useful
calibration
data. Current models are tuned to match the properties of
the
AGB population in the Magellanic Clouds, and thus have only been
calibrated
in a very narrow range of sub-solar metallicities.
Preliminary
observations already suggest that the models are
overestimating
AGB lifetimes by factors of 2-3 at lower metallicities.
At
higher (solar) metallicities, there are no appropriate observations
for
calibrating the models.
We
propose a WFC3/IR SNAP survey of nearby galaxies to create a large
database
of AGB populations spanning the full range of metallicities and
star
formation histories. Because of their intrinsically red colors and
dusty
circumstellar envelopes, tracking the numbers and bolometric
fluxes
of AGB stars requires the NIR observations we propose here. The
resulting
observations of nearby galaxies with deep ACS imaging offer
the
opportunity to obtain large (100-1000's) complete samples of AGB
stars
at a single distance, in systems with well-constrained star
formation
histories and metallicities.
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/UV
12019
After
the Fall: Fading AGN in Post-starburst Galaxies
We
propose joint Chandra and HST observations of an extraordinary sample
of
12 massive post-starburst galaxies at z=0.4-0.8 that are in the
short-lived
evolution phase a few 100 Myr after the peak of
merger-driven
star formation and AGN activity. We will use the data to
measure
X-ray luminosities, black hole masses, and accretion rates; and
with
the accurate "clocks" provided by post-starburst stellar
populations,
we will directly test theoretical models that predict a
power-law
decay in the AGN light curve. We will also test whether star
formation
and black hole accretion shut down in lock-step, quantify
whether
the black holes transition to radiatively inefficient accretion
states,
and constrain the observational signatures of black hole
mergers.
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.
WFC3/UVIS
11595
Turning
Out the Light: A WFC3 Program to Image z>2 Damped Lyman Alpha
Systems
We
propose to directly image the star-forming regions of z>2 damped Lya
systems
(DLAs) using the WFC3/UVIS camera on the Hubble Space Telescope.
In
contrast to all previous attempts to detect the galaxies giving rise
to
high redshift DLAs, we will use a novel technique that completely
removes
the glare of the background quasar. Specifically, we will target
quasar
sightlines with multiple DLAs and use the higher redshift DLA as
a
``blocking filter'' (via Lyman limit absorption) to eliminate all FUV
emission
from the quasar. This will allow us to carry out a deep search
for
FUV emission from the lower redshift DLA, shortward of the Lyman
limit
of the higher redshift absorber. The unique filter set and high
spatial
resolution afforded by WFC3/UVIS will then enable us to directly
image
the lower redshift DLA and thus estimate its size, star- formation
rate
and impact parameter from the QSO sightline. We propose to observe
a
sample of 20 sightlines, selected primarily from the SDSS database,
requiring
a total of 40 HST orbits. The observations will allow us to
determine
the first FUV luminosity function of high redshift DLA
galaxies
and to correlate the DLA galaxy properties with the ISM
characteristics
inferred from standard absorption-line analysis to
significantly
improve our understanding of the general DLA population.
WFC3/UVIS
11786
HST
Observations of Astrophysically Important Visual Binaries
This
is a continuation of a project begun in Cycle 7 and continued up
through
Cycle 14. The program consists of annual FGS or WFPC2
observations
of three visual binary stars that will yield fundamental
astrophysical
results, once their orbits and masses are determined. In
Cycle
17 we are changing WFPC2 to WFC3.
Our
targets are the following: (1) Procyon (P = 40.9 yr), for which our
first
WFPC2 images yielded an extremely accurate angular separation of
the
bright F star and its much fainter white- dwarf companion. Combined
with
ground-based astrometry of the bright star, our observation
significantly
revised downward the derived masses, and brought Procyon A
into
much better agreement with theoretical evolutionary masses for the
first
time. With the continued monitoring proposed here, we will obtain
masses
to an accuracy of better than 1%, providing a testbed for
theories
of both Sun-like stars and white dwarfs. (2) G 107-70, a close
double
white dwarf (P = 18.5 yr) that promises to add two accurate
masses
to the tiny handful of white-dwarf masses that are directly known
from
dynamical measurements. (3) Mu Cas (P = 20.8 yr), a famous nearby
metal-deficient
G dwarf for which accurate masses will lead to the
stars'
helium contents, with cosmological implications. For all three
stars,
we will also be setting increasingly stringent limits on the
presence
of planetary-mass bodies in the systems.
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).
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.
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
7
7
FGS
REAcq
9
9
OBAD
with Maneuver 4
4
SIGNIFICANT
EVENTS: (None)