HUBBLE SPACE TELESCOPE - Continuing to collect World Class
Science
DAILY REPORT #4657
PERIOD COVERED: 5am July 21 - 5am July 22, 2008 (DOY
203/0900z-204/0900z)
OBSERVATIONS SCHEDULED
ACS/SBC 11131
Star Formation at Large Radii in Cooling Flow Brightest
Cluster Galaxies
We propose to take deep ACS FUV images of the bright
central galaxies in
two powerful cooling flow clusters for which we have VLT
UBR images,
with the object of determining whether the UV excesses we
observe at
large radii (>15kpc) are caused by young stars,
ultrahot (WR) stars, or
an as yet unknown source. Current models of excess UV
light at the
AGN-dominated centers of these galaxies cannot easily be
extended to
large radii. New understanding of star formation in these
clusters will
be directly applicable to scenarios of galaxy formation in
the early
universe.
WFPC2 11024
WFPC2 CYCLE 15 INTERNAL MONITOR
This calibration proposal is the Cycle 15 routine internal
monitor for
WFPC2, to be run weekly to monitor the health of the
cameras. A variety
of internal exposures are obtained in order to provide a
monitor of the
integrity of the CCD camera electronics in both bays {both
gain 7 and
gain 15 -- to test stability of gains and bias levels}, a
test for
quantum efficiency in the CCDs, and a monitor for possible
buildup of
contaminants on the CCD windows. These also provide raw
data for
generating annual super-bias reference files for the
calibration
pipeline.
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 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 11547
Characterizing Pre-Main Sequence Populations in Stellar
Associations of
the Large Magellanic Cloud
The Large Magellanic Cloud (LMC) offers an extremely rich
sample of
resolved low-mass stars (below 1 Solar Mass) in the act of
formation
that has not been explored sufficiently yet. These
pre-main sequence
(PMS) stars provide a unique snapshot of the star
formation process, as
it is being recorded for the last ~20 Myr, and they give
important
information on the low-mass Initial Mass Function (IMF) of
their host
stellar systems. Studies of young, rich LMC clusters like
30 Doradus are
crowding limited, even at the angular resolution
facilitated by HST in
the optical. To learn more about low-mass PMS stars in the
LMC, one has
to study less crowded regions like young stellar
associations. We
propose to employ WFPC2 to obtain deep photometry (V ~
25.5 mag) of four
selected LMC stellar associations in order to perform an
original
optical analysis of their red PMS and blue bright MS
stellar
populations. With these observations we aim at a
comprehensive study,
which will add substantial information on the most recent
star formation
and the IMF in the LMC. The data reduction and analysis
will be
performed with a 2D photometry software package especially
developed by
us for WFPC2 imaging of extended stellar associations with
variable
background. Our targets have been selected optimizing a
combination of
criteria, namely spatial resolution, crowding, low
extinction, nebular
contamination, and background confusion in comparison to
other regions
in the Local Group. Parallel NICMOS imaging will provide
additional
information on near-infrared properties of the stellar
population in the
regions surrounding these systems.
NIC3 11545
A NICMOS Survey of Newly-Discovered Young Massive Clusters
We are on the cusp of a revolution in massive star
research triggered by
2MASS and Spitzer/GLIMPSE, and now is the ideal time to
capitalize on
these projects by performing the first survey of massive
stars in young
stellar clusters throughout the Galactic plane. A search
of the 2MASS
and GLIMPSE surveys has produced over 450 newly-identified
massive
stellar cluster candidates in the Galactic plane which are
hidden from
our view at optical wavelengths due to extinction. Here we
propose a
program of 29 orbits to image the most promising candidate
clusters in
broad and narrow band filters using HST/NICMOS. We will be
complementing
these observations with approved Spitzer and Chandra
programs,
numerous approved and planned ground-based spectroscopic
observations,
and state-of-the-art modeling. We expect to substantially
increase the
numbers of massive stars known in the Galaxy, including
main sequence
stars and post-main sequence stars in the Red Supergiant,
Luminous Blue
Variable and Wolf-Rayet stages. Ultimately, this program
will address
many of the fundamental topics in astrophysics: the slope
to the initial
mass function (IMF), an upper-limit to the masses of
stars, the
formation and evolution of the most massive stars,
gamma-ray burst (GRB)
progenitors, the chemical enrichment of the interstellar
medium, and
nature of the first stars in the Universe.
WFPC2 11070
WFPC2 CYCLE 15 Standard Darks - part II
This dark calibration program obtains dark frames every
week in order to
provide data for the ongoing calibration of the CCD dark
current rate,
and to monitor and characterize the evolution of hot
pixels. Over an
extended period these data will also provide a monitor of
radiation
damage to the CCDs.
WFPC2 11113
Binaries in the Kuiper Belt: Probes of Solar System
Formation and
Evolution
The discovery of binaries in the Kuiper Belt and related
small body
populations is powering a revolutionary step forward in
the study of
this remote region. Three quarters of the known binaries
in the Kuiper
Belt have been discovered with HST, most by our snapshot
surveys. The
statistics derived from this work are beginning to yield
surprising and
unexpected results. We have found a strong concentration
of binaries
among low-inclination Classicals, a possible size cutoff
to binaries
among the Centaurs, an apparent preference for nearly
equal mass
binaries, and a strong increase in the number of binaries
at small
separations. We propose to continue this successful
program in Cycle 16;
we expect to discover at least 13 new binary systems,
targeted to
subgroups where these discoveries can have the greatest
impact.
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 11218
Snapshot Survey for Planetary Nebulae in Globular Clusters
of the Local
Group
Planetary nebulae {PNe} in globular clusters {GCs} raise a
number of
interesting issues related to stellar and galactic
evolution. The number
of PNe known in Milky Way GCs, 4, is surprisingly low if
one assumes
that all stars pass through a PN stage. However, it is
likely that the
remnants of stars now evolving in Galactic GCs leave the
AGB so slowly
that any ejected nebula dissipates long before the star
becomes hot
enough to ionize it. Thus there should not be ANY PNe in
Milky Way
GCs--but there are four! It has been suggested that these
PNe are the
result of mergers of binary stars within GCs, i.e., that
they are
descendants of blue stragglers. The frequency of
occurrence of PNe in
external galaxies poses more questions, because it shows a
range of
almost an order of magnitude. I propose a Snapshot survey
aimed at
discovering PNe in the GC systems of Local Group galaxies
more distant
than the Magellanic Clouds. These clusters, some of which
may be much
younger than their counterparts in the Milky Way, might
contain many
more PNe than those of our own galaxy. I will use the
standard technique
of emission-line and continuum imaging, which easily
discloses PNe.
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
07
07
OBAD with
Maneuver
28
28
SIGNIFICANT EVENTS: (None)