HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #4659
PERIOD COVERED: 5am July 23 - 5am July 24, 2008 (DOY 205/0900z-206/0900z)
OBSERVATIONS SCHEDULED
FGS 11212
Filling the Period Gap for Massive Binaries
The current census of binaries among the massive O-type stars is
seriously incomplete for systems in the period range from years to
millennia because the radial velocity variations are too small and the
angular separations too close for easy detection. Here we propose to
discover binaries in this observational gap through a Faint Guidance
Sensor SNAP survey of relatively bright targets listed in the Galactic O
Star Catalog. Our primary goal is to determine the binary frequency
among those in the cluster/association, field, and runaway groups. The
results will help us assess the role of binaries in massive star
formation and in the processes that lead to the ejection of massive
stars from their natal clusters. The program will also lead to the
identification of new, close binaries that will be targets of long term
spectroscopic and high angular resolution observations to determine
their masses and distances. The results will also be important for the
interpretation of the spectra of suspected and newly identified binary
and multiple systems.
NIC1/NIC2/NIC3 11321
NICMOS Cycle 16 Flats Stability
This calibration proposal is the Cycle 16 NICMOS flat field monitor
program. A series of camera 1, 2, & 3 flat fields will be obtained to
monitor the health of the cameras.
NIC1/NIC2/NIC3 8795
NICMOS Post-SAA Calibration - CR Persistence Part 6
A new procedure proposed to alleviate the CR-persistence problem of
NICMOS. Dark frames will be obtained immediately upon exiting the SAA
contour 23, and every time a NICMOS exposure is scheduled within 50
minutes of coming out of the SAA. The darks will be obtained in parallel
in all three NICMOS Cameras. The POST-SAA darks will be non-standard
reference files available to users with a USEAFTER date/time mark. The
keyword 'USEAFTER=date/time' will also be added to the header of each
POST-SAA DARK frame. The keyword must be populated with the time, in
addition to the date, because HST crosses the SAA ~8 times per day so
each POST-SAA DARK will need to have the appropriate time specified, for
users to identify the ones they need. Both the raw and processed images
will be archived as POST-SAA DARKSs. Generally we expect that all NICMOS
science/calibration observations started within 50 minutes of leaving an
SAA will need such maps to remove the CR persistence from the science i
mages. Each observation will need its own CRMAP, as different SAA
passages leave different imprints on the NICMOS detectors.
NIC2 11157
NICMOS Imaging Survey of Dusty Debris Around Nearby Stars Across the
Stellar Mass Spectrum
Association of planetary systems with dusty debris disks is now quite
secure, and advances in our understanding of planet formation and
evolution can be achieved by the identification and characterization of
an ensemble of debris disks orbiting a range of central stars with
different masses and ages. Imaging debris disks in starlight scattered
by dust grains remains technically challenging so that only about a
dozen systems have thus far been imaged. A further advance in this field
needs an increased number of imaged debris disks. However, the technical
challenge of such observations, even with the superb combination of HST
and NICMOS, requires the best targets. Recent HST imaging investigations
of debris disks were sample-limited not limited by the technology used.
We performed a search for debris disks from a IRAS/Hipparcos cross
correlation which involved an exhaustive background contamination check
to weed out false excess stars. Out of ~140 identified debris disks, we
selected 22 best targets in terms of dust optical depth and disk angular
size. Our target sample represents the best currently available target
set in terms of both disk brightness and resolvability. For example, our
targets have higher dust optical depth, in general, than newly
identified Spitzer disks. Also, our targets cover a wider range of
central star ages and masses than previous debris disk surveys. This
will help us to investigate planetary system formation and evolution
across the stellar mass spectrum. The technical feasibility of this
program in two-gyro mode guiding has been proven with on-orbit
calibration and science observations during HST cycles 13, 14, and 15.
NIC3 11107
Imaging of Local Lyman Break Galaxy Analogs: New Clues to Galaxy
Formation in the Early Universe
We have used the ultraviolet all-sky imaging survey currently being
conducted by the Galaxy Evolution Explorer {GALEX} to identify for the
first time a rare population of low-redshift starbursts with properties
remarkably similar to high-redshift Lyman Break Galaxies {LBGs}. These
"compact UV luminous galaxies" {UVLGs} resemble LBGs in terms of
size,
SFR, surface brightness, mass, metallicity, kinematics, dust, and color.
The UVLG sample offers the unique opportunity of investigating some very
important properties of LBGs that have remained virtually inaccessible
at high redshift: their morphology and the mechanism that drives their
star formation. Therefore, in Cycle 15 we have imaged 7 UVLGs using ACS
in order to 1} characterize their morphology and look for signs of
interactions and mergers, and 2} probe their star formation histories
over a variety of timescales. The images show a striking trend of small-
scale mergers turning large amounts of gas into vigorous starbursts {a
process referred to as dissipational or "wet" merging}. Here, we
propose
to complete our sample of 31 LBG analogs using the ACS/SBC F150LP {FUV}
and WFPC2 F606W {R} filters in order to create a statistical sample to
study the mechanism that triggers star formation in UVLGs and its
implications for the nature of LBGs. Specifically, we will 1} study the
trend between galaxy merging and SFR in UVLGs, 2} artificially redshift
the FUV images to z=1-4 and compare morphologies with those in similarly
sized samples of LBGs at the same rest-frame wavelengths in e.g. GOODS,
UDF, and COSMOS, 3} determine the presence and morphology of significant
stellar mass in "pre-burst" stars, and 4} study their immediate
environment. Together with our Spitzer {IRAC+MIPS}, GALEX, SDSS and
radio data, the HST observations will form a unique union of data that
may for the first time shed light on how the earliest major episodes of
star formation in high redshift galaxies came about. This proposal was
adapted from an ACS HRC+WFC proposal to meet the new Cycle 16 observing
constraints, and can be carried out using the ACS/SBC and WFPC2 without
compromising our original science goals.
WFPC2 11156
Monitoring Active Atmospheres on Uranus and Neptune
We propose Snapshot observations of Uranus and Neptune to monitor
changes in their atmospheres on time scales of weeks and months. Uranus
equinox is only months away, in December 2007. Hubble Space Telescope
observations during the past several years {Hammel et al. 2005, Icarus
175, 284 and references therein} have revealed strongly wavelength-
dependent latitudinal structure, the presence of numerous
visible-wavelength cloud features in the northern hemisphere, at least
one very long-lived discrete cloud in the southern hemisphere, and in
2006 the first dark spot ever seen on Uranus. Long-term ground-based
observations {Lockwood and Jerzekiewicz, 2006, Icarus 180, 442; Hammel
and Lockwood 2007, Icarus 186, 291} reveal seasonal brightness changes
whose origins are not well understood. Recent near- IR images of
obtained using adaptive optics on the Keck Telescope, together with HST
observations {Sromovsky et al. 2003, Icarus 163, 256 and references
therein} which include previous Snapshot programs {GO 8634, 10170,
10534} show a general increase in activity at south temperate latitudes
until 2004, when
Further Snapshot observations of these two dynamic planets will
elucidate the nature of long-term changes in their zonal atmospheric
bands and clarify the processes of formation, evolution, and dissipation
of discrete albedo features.
WFPC2 11544
The Dynamical Legacy of Star Formation
We propose to use WFPC2 to conduct a wide-field imaging survey of the
young cluster IC348. This program, in combination with archival HST
observations, will allow us to measure precise proper motions for
individual cluster members, characterizing the intra-cluster velocity
dispersion and directly studying the dynamical signatures of star
formation and early cluster evolution. Our projected astrometric
precision (~1 mas in each epoch) will allow us to calculate individual
stellar velocities to unprecedented precision (<0.5 mas/yr; <1 km/s) and
directly relate these velocities to observed spatial substructure within
the cluster. This survey will also allow us to probe small-scale star
formation physics by searching for high-velocity stars ejected from
decaying multiple systems, expanding our knowledge of multiplicity in
dense environments, and identifying new substellar and planetary-mass
cluster members based on kinematic membership tests.
WFPC2/NIC2 11173
Completing an Accurate Map of M31 Microlensing
The halo microlensing masses detected in the MACHO survey (claimed to
compose about 20% of the Galaxy's mass) represent a major enigma in
astrophysics, one that must be effectively cross-examined by an
independent test. We have completed a large, densely-sampled survey of
M31 that can reveal in another galaxy such a halo microlensing signal if
it exists. In a previous HST/ACS+WFPC2 program (GO 10273, Cycle 13, 16
orbits) we were able to learn considerably more about a subsample of
these M31 microlensing events. We were pleased to find that in most
cases we could isolate the source star for each event, find its baseline
flux and colors (essential for ruling out classes of confusing variable
stars), test for misidentification of background supernovae, and measure
the Einstein parameters, which constrain the range of most likely lens
mass. (These Cycle 13 results are published in The Astrophysical Journal
Letters.) We propose to finish the job, taking a similar series of
exposures to more than double the sample of well-constrained
microlensing events, which together with the larger ground-based sample
for which we are completing our analyses will provide 20-30 M31 bona
fide microlensing events observed by HST. This will be done via a series
of targeted PC exposures, meant to maximize the number of candidates
studied, one (or two) at a time. A sample of this size and quality
should be sufficient to settle the issue of a significant contribution
to the halos of galaxies by stellar-mass lenses. Furthermore, if there
is a surplus of such microlensing events above what might be expected
from stars alone, the higher quality of information will allow us to
more accurately describe the spatial distribution of these lenses. We
will also complete several unique studies of M31 stellar populations,
both in support of the microlensing measurement and in their own right.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports
of potential non-nominal performance that will be investigated.)
HSTARS:
#11406 GSACQ(2,3,2) fine lock backup on FGS2 during LOS @205/11:59:26z
QF3STOPF and QSTOP
flags were set on FGS 3. Post acquisition
Observations
affected: ACS #3, Proposal #11107; and NICMOS #47,
Proposal #08795.
#11408 GSAcq(2,3,2) failed to RGA Hold (Gyro Control) @205/18:53:30z
due to a Search
Radius Limit Exceeded Error on FGS-2. Also received
"T2G OPEN LOOP
TIMEOUT" and "TxG FHST SANITY CHECK FAILED" ESB
errors.
Observations affected: WFPC #91-94, Proposal ID#11173.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED
SUCCESSFUL
FGS GSacq
14
13
FGS REacq
0
0
OBAD with Maneuver 28
26
SIGNIFICANT EVENTS: (None)