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 # 4462
PERIOD
COVERED: UT October 04, 2007 (DOY 277)
OBSERVATIONS
SCHEDULED
ACS/SBC
WFPC2 11175
UV
Imaging to Determine the Location of Residual Star Formation in
Galaxies
Recently Arrived on the Red Sequence
We
have identified a sample of low-redshift {z = 0.04 - 0.10} galaxies
that
are candidates for recent arrival on the red sequence. They have
red
optical colors indicative of old stellar populations, but blue
UV-optical
colors that could indicate the presence of a small quantity
of
continuing or very recent star formation. However, their spectra lack
the
emission lines that characterize star-forming galaxies. We propose
to
use ACS/SBC to obtain high- resolution imaging of the UV flux in
these
galaxies, in order to determine the spatial distribution of the
last
episode of star formation. WFPC2 imaging will provide B, V, and I
photometry
to measure the main stellar light distribution of the galaxy
for
comparison with the UV imaging, as well as to measure color
gradients
and the distribution of interstellar dust. This detailed
morphological
information will allow us to investigate the hypothesis
that
these galaxies have recently stopped forming stars and to compare
the
observed distribution of the last star formation with predictions
for
several different mechanisms that may quench star formation in
galaxies.
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.
NIC3
11080
Exploring
the Scaling Laws of Star Formation
As
a variety of surveys of the local and distant Universe are
approaching
a full census of galaxy populations, our attention needs to
turn
towards understanding and quantifying the physical mechanisms that
trigger
and regulate the large-scale star formation rates {SFRs} in
galaxies.
WFPC2
11029
WFPC2
CYCLE 15 Intflat Linearity Check and Filter Rotation Anomaly
Monitor
Intflat
observations will be taken to provide a linearity check: the
linearity
test consists of a series of intflats in F555W, in each gain
and
each shutter. A combination of intflats, visflats, and earthflats
will
be used to check the repeatability of filter wheel motions.
{Intflat
sequences tied to decons, visits 1-18 in prop 10363, have been
moved
to the cycle 15 decon proposal xxxx for easier scheduling.} Note:
long-exposure
WFPC2 intflats must be scheduled during ACS anneals to
prevent
stray light from the WFPC2 lamps from contaminating long ACS
external
exposures.
WFPC2
11079
Treasury
Imaging of Star Forming Regions in the Local Group:
Complementing
the GALEX and NOAO Surveys
We
propose to use WFPC2 to image the most interesting star-forming
regions
in the Local Group galaxies, to resolve their young stellar
populations.
We will use a set of filters including F170W, which is
critical
to detect and characterize the most massive stars, to whose hot
temperatures
colors at longer wavelengths are not sensitive. WFPC2's
field
of view ideally matches the typical size of the star-forming
regions,
and its spatial resolution allows us to measure individual
stars,
given the proximity of these galaxies. The resulting H-R diagrams
will
enable studies of star-formation properties in these regions, which
cover
largely differing metallicities {a factor of 17, compared to the
factor
of 4 explored so far} and characteristics. The results will
further
our understanding of the star-formation process, of the
interplay
between massive stars and environment, the properties of dust,
and
will provide the key to interpret integrated measurements of
star-formation
indicators {UV, IR, Halpha} available for several
hundreds
more distant galaxies. Our recent deep surveys of these
galaxies
with GALEX {FUV, NUV} and ground-based imaging {UBVRI, Halpha,
[OIII]
and [SII]} provided the identification of the most relevant SF
sites.
In addition to our scientific analysis, we will provide catalogs
of
HST photometry in 6 bands, matched corollary ground-based data, and
UV,
Halpha and IR integrated measurements of the associations, for
comparison
of integrated star-formation indices to the resolved
populations.
We envisage an EPO component.
WFPC2
11103
A
Snapshot Survey of The Most Massive Clusters of Galaxies
We
propose the continuation of our highly successful SNAPshot survey of
a
sample of 125 very X-ray luminous clusters in the redshift range
0.3-0.7.
As demonstrated by the 25 snapshots obtained so far in Cycle14
and
Cycle15 these systems frequently exhibit strong gravitational
lensing
as well as spectacular examples of violent galaxy interactions.
The
proposed observations will provide important constraints on the
cluster
mass distributions, the physical nature of galaxy-galaxy and
galaxy-gas
interactions in cluster cores, and a set of optically bright,
lensed
galaxies for further 8-10m spectroscopy. All of our primary
science
goals require only the detection and characterisation of
high-surface-brightness
features and are thus achievable even at the
reduced
sensitivity of WFPC2. Because of their high redshift and thus
compact
angular scale our target clusters are less adversely affected by
the
smaller field of view of WFPC2 than more nearby systems.
Acknowledging
the broad community interest in this sample we waive our
data
rights for these observations. Due to a clerical error at STScI our
approved
Cycle15 SNAP program was barred from execution for 3 months and
only
6 observations have been performed to date - reinstating this SNAP
at
Cycle16 priority is of paramount importance to reach meaningful
statistics.
WFPC2
11129
The
Star Formation History of the Fornax Dwarf Spheroidal Galaxy
The
Fornax dwarf spheroidal galaxy is one of the most luminous dwarf
satellites
of the Milky Way. It is unusual in many ways: it hosts 5
globular
clusters, shows some relatively young stars, and has faint
sub-structures
which have been interpreted as signs of recent
interactions.
It is thus of great interest to learn the complete star
formation
history {SFH} of Fornax to establish a link between its
evolutionary
path and the predictions from numerical simulations, as a
test
of our understanding of dwarf galaxy evolution. Yet many questions
remain
open. Is the old stellar population made up of stars formed in a
very
early burst, perhaps before the epoch of reionisation, or the
result
of a more continuous star formation between 13 and 9 Gyr ago ?
How
quickly did Fornax increase its metallicity during its initial
assembly
and during subsequent episodes of star formation ? Are
accretion
episodes required to explain the age-metallicity history of
Fornax
? However, there has never been a comprehensive study of the
global
SFH of the Fornax field based on data of sufficient depth to
unambiguously
measure the age mixture of the stellar populations and
their
spatial variation. We propose to use the WFPC2 to obtain very deep
images
in several fields across the central region of Fornax in order to
reach
the oldest main-sequence turnoffs. The number of fields is
determined
by the need to measure the SFH over different regions with
distinct
kinematics and metallicity. The resolution achievable with HST
is
crucial to answer these questions because, to derive the age
distribution
of the oldest stars, we are interested in I magnitude
differences
of the order 0.2 mag in crowded fields at V=24.5. We will
directly
measure the time variation in star-formation rate over the
entire
galaxy history, from first stars coeval with the Milky Way halo
to
the youngest populations 200 Myr ago. The combination of detailed CMD
analysis
with WFPC2 with our existing metallicity and kinematic
information
will allow us to trace out the early phases of its
evolution.
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
07
07
FGS
REacq
06
06
OBAD
with Maneuver
26
26
SIGNIFICANT
EVENTS: (None)