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24 April 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT #3348

PERIOD COVERED:  DOY 113

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. 

ACS 9293

Massive Black Holes in Early Type Galaxies

3x10^6 Msun < M_BH < 3x10^9 Msun} at the centers of galaxies and the
velocity dispersions of their bulges. However, uncertainties over the
exact slope of the correlation still remain, and it is not known if
such a relation extends to black holes of lower and higher masses.
The discovery of small {r ~ a few hundred pc}, well defined, dust and
gas disks in the nuclei of some active elliptical galaxies opened a
new avenue for measuring central mass distributions. When ionized gas
is present, a small number of high spatial resolution {e.g. STIS}
spectra are sufficient to characterize the disk dynamics and the
galaxy's central mass {e.g., M87, M81, NGC 4374}. We propose to use
STIS spectroscopy to measure black hole masses, using gas dynamics,
in the centers of several brightest cluster galaxies {BCGs}, 2 nearby
galaxies with low velocity dispersions, and a number of elliptical
galaxies known to harbor small nuclear dust disks. The proposed
targets encompass a wide range of black hole masses, allowing us to
fully examine the M_BH -- sigma relationship. We will also obtain
H-alpha and continuum images to fully characterize the gaseous and
dust morphology as well as stellar surface profile in the central
regions. 

ACS 9299

Geometric Measurement of Galaxy Distances

We propose to utilize the imaging polarization capability of ACS to
make observations of supernova light echoes in an investigation of
their potential use for the geometric determination of galaxy
distances. SN1991T in NGC4527 is a confirmed light echo close to the
Virgo galaxy cluster. We will visit it twice, once early in the
mission and then later to monitor its evolution. We will also obtain
high resolution imaging polarization observations of other candidates
to determine whether they are light echoes and to use them for
distance estimation if possible. We will also acquire a deep field
image in polarized light of a galaxy known to have hosted large
numbers of historical supernovae. We will search for light echoes,
plerions and other sources of polarized emission in the targets such
as reflection nebulosity, light polarized by transmission through
aligned grains, light echoes from other transients or variable stars
and light scattering from the nucleus.

STIS 9369

A Direct Test for Dust-driven Wind Physics

We propose to perform with STIS a critical test of the physical
mechanism of wind acceleration by dust drag in cool stars. Spatially
resolved spectra of the circumstellar environment of Alpha Ori {M2
Iab} will directly test if radiation pressure onto dust grains
provides the momentum that causes the high mass-loss rates {up to
10^-6 M_odot yr^-1} observed in asymptotic giant branch and red
supergiant stars. Terminal gas outflow velocities of 13-14 km, s^-1
are observed in Betelgeuse's circumstellar dust shell. However, the
smaller chromospheric outflow velocities {below 6 km, s^- 1}, point
to an extended region in the circumstellar environment where the
wind accelerates. Stellar wind theory suggests radiation pressure
onto dust grains as the driving mechanism that drags the gas outflow
to these high terminal velocities. Dynamic radiative transport
calculations that fit the star's 9.7 Mum silicate dust emission
indicate that this wind accelerating region is located between 0.78"
and ~3". We propose to use STIS to obtain a high-resolution spatial
and spectral raster scan across this region.  These data can only be
obtained for this unique nearby supergiant with the exceptional
capabilities of the STIS. An increase of the observed asymmetry of
the self-absorbed Mg ii h line {which forms in an expanding gas
shell} with distance from the star, will directly confirm {or reject}
the theory of dust-driven wind acceleration in cool stars.

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. 

 - Continued -

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