Daily Report #4657

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 images. 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 OB 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
Neptune 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 Neptune returned to a rather Voyager-like
appearance. 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
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SIGNIFICANT EVENTS: (None)