Daily Rpt #4680

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT*** #4680

PERIOD COVERED: 5am August 21 - 5am August 22, 2008 (DOY
234/0900z-235/0900z)

OBSERVATIONS SCHEDULED

NIC1 11136

Resolving Ultracool Astrophysics with Brown Dwarf Binaries

We propose to obtain resolved far-red and near-IR photometry of 13
brown dwarf binaries with HST/NICMOS in order to study one of the
long-standing puzzles in ultracool astrophysics, namely the rapid
change in spectra from L dwarfs to T dwarfs at nearly constant
effective temperature (a.k.a. the "L/T transition''). While many
nearby brown dwarfs have been studied, use of such samples is
inevitably hindered by the unknown ages, masses, and metallicities of
the field population. Characterization of resolved ultracool binaries
is a promising avenue for addressing this problem, by providing coeval
systems of the same composition with comparable masses and
temperatures. Our proposed HST/NICMOS (0.9-1.6 micron) observations
will be combined with longer wavelength ground-based photometry and
spectroscopy from Keck laser guide star adaptive optics. The resulting
multiband (0.9-2.5 micron) dataset will be a unique resource for
measuring the evolution of spectral energy distributions across the
L/T transition, to test state-of-the-art atmospheric models, and to
determine the physical process(es) that dominate the L/T transition.
Understanding the L/T transition is important not only for testing
brown dwarf atmospheres, but also provides a key pathway for
understanding the same physical effects, namely the formation and
removal of clouds, in the atmospheres of the extrasolar planets.

NIC1 11205

The Effects of Multiplicity on the Evolution of Young Stellar Objects:
A NICMOS Imaging Study

We propose to use NICMOS to investigate the multiplicity of young
stellar objects (YSOs) in the Orion B molecular cloud. Previous
observations with the Spitzer Space Telescope have revealed a
remarkable star forming filament near the NGC 2068 reflection nebula.
The population of YSOs associated with the filament exhibit a
surprisingly wide range of circumstellar evolutionary states, from
deeply embedded protostars to T Tauri accretion disks. Many of the
circumstellar disks themselves show evidence for significant dust
evolution, including grain growth and settling and cleared inner
holes, apparently in spite of the very young age of these stars. We
will estimate the binary fraction of a representative sample of
objects in these various stages of evolution in order to test whether
companions may play a significant role in that evolution.

NIC1/NIC2/NIC3 11330

NICMOS Cycle 16 Extended Dark

This takes a series of Darks in parallel to other instruments.

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 11101

The Relevance of Mergers for Fueling AGNs: Answers from QSO Host
Galaxies

The majority of QSOs are known to reside in centers of galaxies that
look like ellipticals. Numerical simulations have shown that remnants
of galaxy mergers often closely resemble elliptical galaxies. However,
it is still strongly debated whether the majority of QSO host galaxies
are indeed the result of relatively recent mergers or whether they are
completely analogous to inactive ellipticals to which nothing
interesting has happened recently. To address this question, we
recently obtained deep HST ACS images for five QSO host galaxies that
were classified morphologically as ellipticals {GO-10421}. This pilot
study revealed striking signs of tidal interactions such as ripples,
tidal tails, and warped disks that were not detected in previous
studies. Our observations show that at least some "elliptical" QSO
host galaxies are the products of relatively recent merger events
rather than old galaxies formed at high redshift. However, the
question remains whether the host galaxies of classical QSOs are truly
distinct from inactive ellipticals and whether there is a connection
between the merger events we detect and the current nuclear activity.
We must therefore place our results into a larger statistical context.
We are currently conducting an HST archival study of inactive
elliptical galaxies {AR- 10941} to form a control sample. We now
propose to obtain deep HST/WFPC2 images of 13 QSOs whose host galaxies
are classified as normal ellipticals. Comparing the results for both
samples will help us determine whether classical QSOs reside in normal
elliptical galaxies or not. Our recent pilot study of five QSOs
indicates that we can expect exciting results and deep insights into
the host galaxy morphology also for this larger sample of QSOs. A
statistically meaningful sample will help us determine the true
fraction of QSO hosts that suffered strong tidal interactions and
thus, whether a merger is indeed a requirement to trigger nuclear
activity in the most luminous AGNs. In addition to our primary science
observations with WFPC2, we will obtain NICMOS3 parallel observations
with the overall goal to select and characterize galaxy populations at
high redshifts. The imaging will be among the deepest NICMOS images:
These NICMOS images are expected to go to a limit a little over 1
magnitude brighter than HUDF-NICMOS data, but over 13 widely separated
fields, with a total area about 1.5 times larger than HUDF- NICMOS.
This separation means that the survey will tend to average out effects
of cosmic variance. The NICMOS3 images will have sufficient resolution
for an initial characterization of galaxy morphologies, which is
currently one of the most active and promising areas in approaching
the problem of the formation of the first massive galaxies. The depth
and area coverage of our proposed NICMOS observations will also allow
a careful study of the mass function of galaxies at these redshifts.
This provides a large and unbiased sample, selected in terms of
stellar mass and unaffected by cosmic variance, to study the on-going
star formation activity as a function of mass {i.e. integrated star
formation} at this very important epoch.

NIC3 11334

NICMOS Cycle 16 Spectrophotometry

Observation of the three primary WD flux standards must be repeated to
refine the NICMOS absolute calibration and monitor for sensitivity
degradation. So far, NICMOS grism spectrophotometry is available for
only ~16 stars with good STIS spectra at shorter wavelengths. There
are more in the HST CALSPEC standard star data base with good STIS
spectra that would also become precise IR standards with NICMOS
absolute SED measurements. Monitoring the crucial three very red stars
(M, L, T) for variability and better S/N in the IR. Apparent
variability was discovered at shorter wavelengths during the ACS
cross-calibration work that revealed a ~2% discrepancy of the cool
star fluxes with respect to the hot primary WD standards. About a
third of these stars are bright enough to do in one orbit, the rest
require 2 orbits.

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 11221

A Dark Core in Abell 520

We have recently discovered that the rich cluster Abell 520 exhibits
truly extreme multi-wavelength characteristics. The data indicate that
the cluster is the site of a major merger. Our weak lensing analysis,
based on a deep CFHT image, suggests the presence of a massive dark
core that coincides with the central X-ray emission peak, while being
largely devoid of galaxies. Although a displacement between the X-ray
gas and the galaxy/dark matter distribution may be expected in a
merger (e.g. as in the bullet cluster), the dark matter peak without
galaxies cannot be easily explained within the current collisionless
dark matter paradigm. A higher resolution mass map is required to make
further progress, as it will enable us to examine the detailed
structure of the dark matter distribution, as well as improve the
significance of the dark peak. We propose a 3 x 3 WFPC2 mosaic of
interlaced images, where each pointing consists of two sets of F814W
exposures offset by 5.5 pixels. This will precisely pinpoint the
locations of the highest lensing peaks, enhance the comparison with
the Chandra X-ray data, and test physical and geometrical models for
the spatial and thermal structure of this remarkable cluster derived
from our suite of gas+dark matter simulations of head-on/off-axis
cluster mergers.

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*********************** 08************* 08
OBAD with Maneuver************** 30************* 30

SIGNIFICANT EVENTS: (None)