Notice:
Due to the conversion of some ACS WFC or HRC observations into
WFPC2,
or NICMOS observations after the loss of ACS CCD science
capability
in January, there may be an occasional discrepancy between a
proposal's
listed (and correct) instrument usage and the abstract that
follows
it.
HUBBLE
SPACE TELESCOPE - Continuing to collect World Class Science
DAILY
REPORT # 4469
PERIOD
COVERED: UT October 16, 2007 (DOY 289)
OBSERVATIONS
SCHEDULED
WFPC2
10925
Imaging
the Nearest Damped Lyman Alpha Absorbers
We
propose to acquire broad-band and H-alpha imaging of three bright,
very
nearby host galaxies for damped Ly-alpha absorbers {DLAs}. Our
targets
are the only DLA hosts at z < 0.03 {i.e., spatial resolutions of
<
1.2 kpc}. The purpose of these observations is to discover the
detailed
morphology and kinematics and thus the origins of the gas
giving
rise to DLAs. While ground-based spectroscopy of DLAs is used to
infer
indirectly the evolution of galaxy metallicity and thick disk
kinematics
out to z > 4, only with HST imaging of the very lowest
redshift
DLA galaxies can we discover these relationships directly. In
conjunction
with H I 21-cm VLA emission maps, broad-band and H-alpha
images
of these DLAs will allow us to determine: {1} the sites of active
star
formation in the host galaxies and their relationship to the QSO
sightline,
{2} the presence of stellar streams, supernova shells, or
bipolar
"superwind" outflows in DLA host galaxies, and {3} the detailed
spiral
structure of the host galaxies, which will allow us to use the
lower
resolution H I 21-cm emission line images to determine unambiguous
DLA
kinematics with respect to the host galaxy {i.e., is the DLA
rotating
with the disk?}. Thus, the high resolution imaging will allow
us
to correctly interpret the kinematics and metallicity information
provided
by the H I 21-cm VLA maps and HST UV spectroscopy to better
inform
the high-z results.
WFPC2
11141
White
dwarfs in the open star cluster NGC 188
White
dwarf cooling sequences represent the only ways in which we can
determine
ages of Galactic components such as the disk and the halo, and
they
are an independent check on main sequence ages of globular star
clusters.
These age measurements rely heavily on theoretical cooling
models,
many of which disagree by as much as a few gigayears for the
coolest
white dwarfs. Further, observations of the white dwarf sequence
in
the super metal- rich open cluster NGC 6791 have found a white dwarf
age
several gigayears younger than the accepted cluster age determined
by
main-sequence fitting. The white dwarf sequence of the
solar-metallicity,
7-Gyr old open cluster NGC 188 can provide some
much-needed
insight into these uncertainties, but previous HST
observations
were too shallow to detect the oldest, faintest white
dwarfs
in the cluster. We propose deep imaging of two fields at the
center
of the cluster with the following goals: {1} To detect the end of
the
white dwarf cooling sequence, providing a much-needed empirical data
point
for cool white dwarf evolutionary models, {2} to compare the white
dwarf
luminosity function of NGC 188 with that of NGC 6791 to determine
if
the odd white dwarf sequence in the latter cluster is due to the
cluster's
high metallicity or due to a shortcoming in theoretical
models,
and {3} to determine via photometry the masses of white dwarfs
formed
by solar-mass stars, a quantity not yet empirically measured.
WFPC2
11178
Probing
Solar System History with Orbits, Masses, and Colors of
Transneptunian
Binaries
The
recent discovery of numerous transneptunian binaries {TNBs} opens a
window
into dynamical conditions in the protoplanetary disk where they
formed
as well as the history of subsequent events which sculpted the
outer
Solar System and emplaced them onto their present day heliocentric
orbits.
To date, at least 47 TNBs have been discovered, but only about a
dozen
have had their mutual orbits and separate colors determined,
frustrating
their use to investigate numerous important scientific
questions.
The current shortage of data especially cripples scientific
investigations
requiring statistical comparisons among the ensemble
characteristics.
We propose to obtain sufficient astrometry and
photometry
of 23 TNBs to compute their mutual orbits and system masses
and
to determine separate primary and secondary colors, roughly tripling
the
sample for which this information is known, as well as extending it
to
include systems of two near-equal size bodies. To make the most
efficient
possible use of HST, we will use a
optimally
schedule our observations.
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 04 04
FGS
REacq 11 11
OBAD
with Maneuver 30 30
SIGNIFICANT
EVENTS:
Gyro
2’s second flex lead failed on DOY (278) 10/05/07. An increase in
the
gyro’s heater duty cycle from 10-12% to 26-38% revealed that
additional
heater power was compensating for the absence of motor
current.
The second flex lead failure was expected. The first flex lead
failed
on August 31, 2007, after which Gyro 6 was turned on. The second
flex
lead’s failure did not impact HST’s operation.