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29 April 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT        # 3351

PERIOD COVERED: DOY 118

Part 1 of 3

OBSERVATIONS SCHEDULED

NICMOS 8791

NICMOS Post-SAA calibration - CR Persistence Part 2

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.

WFPC2 9033

Measuring the mass distribution in the most distant, very X-ray
luminous galaxy cluster known

distribution in the massive, distant galaxy cluster ClJ1226.9+3332,
recently discovered by us. At z=0.888 this exceptional system is more
X-ray luminous and more distant than both MS1054.4-0321 and
ClJ0152.7-1357, the previous record holders, thus providing yet
greater leverage for cosmological studies of cluster evolution.
ClJ1226.9+3332 differs markedly from all other currently known
distant clusters in that it exhibits little substructure and may even
host a cooling flow, suggesting that it could be the first cluster to
be discovered at high redshift that is virialized. We propose joint
HST and Chandra observations to investigate the dynamical state of
this extreme object. This project will 1} take advantage of HST's
superb resolution at optical wavelengths to accurately map the mass
distribution within 1.9 h^{-1} 50 Mpc via strong and weak
gravitational lensing, and 2} use Chandra's unprecedented resolution
in the X-ray waveband to obtain independent constraints on the gas
and dark matter distribution in the cluster core, including the
suspected cooling flow region. As a bonus, the proposed WFPC2
observations will allow us to test the results by van Dokkum et al.
{1998, 1999} on the properties of cluster galaxies {specifically
merger rate and morphologies} at z~0.8 from their HST study of
MS1054.4-0321.

NICMOS 9386

Infrared Photometry of a Statistically Significant Sample of KBOs

of the solar system has been slowed by a lack of basic astrophysical
data. Photometric observations of the majority of the more than 400
known KBOs and Centaurs are rudimentary and incomplete, particularly
in the infrared. The multicolor optical-infrared photometry that
exists for a small subset of KBOs often shows significant
discrepancies between observations by different observers. Their
intrinsic faintness puts them at the practical limits of ground-based
systems. In July 2001 we began what will be the largest uniform
sample of optical photometry of KBOs with a WFPC2 SNAPSHOT program
that will perform accurate photometry at V, R, and I on a sample of
up to 150 targets. We seek to greatly enhance the value of this
survey by obtaining J and H photometry on the same sample using
NICMOS. Combined optical and infrared broad band photometry is a far
more powerful tool for physical studies than is either alone. Our
sample includes objects that will be observed at thermal infrared
wavelengths by SIRTF and will be used with those data to derive the
first accurate diameters, albedos, and surface properties for a large
sample of KBOs.

ACS 9401

The ACS Virgo Cluster Survey

We propose the most comprehensive imaging survey to date of
low-redshift, early-type galaxies. Our goal is to exploit the
exceptional imaging capabilities of the ACS by acquiring deep
images --- in the SDSS g^ and z^ bandpasses --- for 163 E, S0, dE,
dE, N and dS0 galaxies in Virgo, the nearest rich cluster. This
extraordinary dataset would likely constitute one of the principal
legacies of HST, and would have widespread applications for many
diverse areas of astrophysics. Our immediate scientific objectives
are threefold: {1} measure metallicities, ages and radii for the many
thousands of globular clusters {GCs} in these galaxies, and use this
information to derive the protogalactic mass spectrum of each
galaxy; {2} measure the central luminosity and color profile of
each galaxy, and use this information to carry out a completely
independent test of the merging hierarchy inferred from the GCs, with
the aid of N-body codes that simulate the merger of galaxies
containing massive black holes; and {3} calibrate the z^ -band SBF
method, measure Virgo's 3-D structure, and carry out the definitive
study of the GC luminosity function's precision as a standard candle.
Our proposed Virgo Cluster Survey will yield a database of
unprecedented depth, precision and uniformity, and will enable us to
study the record of galaxy and cluster formation in a level of detail
which will never be possible with more distant systems.

STIS 9437

Quantitative Constraints for Massive Star Evolution Models with
Rotation

Rotation is now recognized as an important physical component in
understanding massive stars. Theory suggests that rotation affects
the lifetimes, chemical yields, stellar evolution tracks, and the
supernova and compact remnant properties {Heger & Langer 2000,
Maeder & Meynet 2000}. In a Cycle 7 program, we proved that
rotational mixing occurs in massive main sequence stars {Venn et al.
2001}. In this proposal, we want to quantitatively test model
predictions and constrain the theory for a better understanding of
massive star evolution. We are requesting HST STIS observations of
the BIII 2066 Angstrom resonance line of seven massive stars in three
young clusters carefully selected from IUE analyses. These stars show
traces of boron depletion, but without nitrogen enrichment; rotation
is the only theory able to explain this abundance pattern. These new
abundances will allow us to test rotating model predictions: that
mixing strength increases with stellar age, mass, and rotation rate.
They will also help to quantitatively constrain the rotational mixing
efficiencies in massive stars. One very high S/N spectrum of a
moderately boron-depleted star is also requested. We wish to measure
its 11B/10B ratio, which is predicted to change as boron is depleted
in the rotating models. This ratio will further confirm rotational
effects and observationally constrain the 10B{p, Alpha} thermonuclear
reaction rate, which is presently highly uncertain. 

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