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HUBBLE SPACE TELESCOPE

DAILY REPORT # 3361

PERIOD COVERED: DOY 132

OBSERVATIONS SCHEDULED

NICMOS 8791

Part 1 of 2

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/WFC/HRC 9075

Cosmological Parameters from Type Ia Supernovae at High Redshift.

The Advanced Camera for Surveys (WFC and HRC) was used to obtain a
Hubble diagram of Type Ia supernovae {SNe Ia} that will be of long
lasting value as a record of the expansion history of the universe.

STIS/CCD 9186

D/H in Lyman Limit Absorbers with Simple Velocity Structure.

The Space Telescope Imaging Spectrograph (CCD) was used to observe
the deuterium abundance in QSO absorbers that provides a direct
measurement of the baryonic density of the Universe. This proposal
will obtain new high resolution data of two carefully selected,
intermediate redshift absorption systems. 

NICMOS/STIS CCD 9405

The Origin of Gamma-Ray Bursts

The rapid and accurate localization of gamma-ray bursts {GRBs}
promised by a working HETE-2 during the coming year may well
revolutionize our ability to study these enigmatic, highly luminous
transients. We propose a program of HST and Chandra observations to
capitalize on this extraordinary opportunity. We will perform some of
the most stringent tests yet of the standard model, in which GRBs
represent collimated relativistic outflows from collapsing massive
stars. NICMOS imaging and STIS CCD spectroscopy will detect broad
atomic features of supernovae underlying GRB optical transients, at
luminosities more than three times fainter than SN 1998bw. UV,
optical, and X-ray spectroscopy will be used to study the local ISM
around the GRB. Chandra spectroscopy will investigate whether the GRB
X-ray lines are from metals freshly ripped from the stellar core by
the GRB. HST and CTIO infra-red imaging of the GRBs and their hosts
will be used to determine whether `dark' bursts are the product of
unusually strong local extinction; imaging studies may for the first
time locate the hosts of `short' GRBs. Our early polarimetry and
late-time broadband imaging will further test physical models of the
relativistic blast wave that produces the bright GRB afterglow, and
will provide unique insight into the influence of the GRB environment
on the afterglow. 

ACS 9463

Are OH/IR stars the youngest post-AGB stars? An ACS SNAPshot imaging
survey 

Essentially all well-characterized preplanetary nebulae {PPNs}--
objects in transition between the AGB and planetary nebula
evolutionary phases - are bipolar, whereas the mass-loss envelopes of
AGB stars are strikingly spherical. In order to understand the
processes leading to bipolar mass-ejection, we need to know at what
stage of stellar evolution does bipolarity in the mass-loss first
manifest itself? We have recently hypothesized that most OH/IR stars
{evolved mass- losing stars with OH maser emission} are very young
PPNe. We propose an ACS/SNAPshot imaging survey of a large,
morphologically unbiased sample of these objects, selected using
their IRAS 12-to-25micron colors. Our ground-based imaging study of
OH/IR stars has revealed a few compact bipolar objects, supporting
our hypothesis. However since most objects remain unresolved, HST
observations are needed to determine how and when the bipolar
geometry asserts itself. Our complementary program of interferometric
mapping of the OH maser emission in our sources is yielding kinematic
information with spatial resolution comparable to that in the HST
images. The HST/radio data will provide crucial input for theories of
post-AGB stellar evolution. In addition, these data will also
indicate whether the multiple concentric rings, ``searchlight
beams'', and truncated equatorial disks recently discovered with HST
in a few PPNs, are common or rare phenomena. 

ACS 9468

ACS Grism Parallel Survey of Emission- line Galaxies at Redshift
z pl 7

We propose an ACS grism parallel survey to search for emission-line
galaxies toward 50 random lines of sight over the redshift interval
0 < zpl 7. We request ACS parallel observations of duration more
than one orbit at high galactic latitude to identify ~ 300 HAlpha
emission-line galaxies at 0.2pl zpl 0.5, ~ 720 O IILambda3727
emission-line galaxies at 0.3pl zpl 1.68, and pg 1000 Ly-alpha
emission-line galaxies at 3pl zpl 7 with total emission line flux
fpg 2* 10^-17 ergs s^-1 cm^-2 over 578 arcmin^2. We will obtain
direct images with the F814W and F606W filters and dispersed images
with the WFC/G800L grism at each position. The direct images will
serve to provide a zeroth order model both for wavelength calibration
of the extracted 1D spectra and for determining extraction apertures
of the corresponding dispersed images. The primary scientific
objectives are as follows: {1} We will establish a uniform sample of
HAlpha and O II emission-line galaxies at z<1.7 in order to obtain
accurate measurements of co-moving star formation rate density versus
redshift over this redshift range. {2} We will study the spatial and
statistical distribution of star formation rate intensity in
individual galaxies using the spatially resolved emission-line
morphology in the grism images. And {3} we will study high-redshift
universe using Ly-alpha emitting galaxies identified at z pl 7 in
the survey. The data will be available to the community immediately
as they are obtained.

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