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3\05 HST Daily Rpt No 3313
Part 1 of 4

 HUBBLE SPACE TELESCOPE
  DAILY REPORT # 3313

PERIOD COVERED: DOY 64

OBSERVATIONS SCHEDULED

WF/PC-2 8669

Merger-Driven Evolution Of Galactic Nuclei: Observations Of The Toomre 
Sequence.

The WF/PC-2 was used to observe galaxy mergers that are believed 
responsible for triggering starburst and AGN activity in galaxies, and 
even perhaps transforming spiral galaxies into ellipticals.

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 9352

The Deceleration Test from Treasury Type Ia Supernovae at Redshifts 
1.2 to 1.6

Type Ia supernovae {SNe Ia} provide the only direct evidence for an 
accelerating universe, an extraordinary result that needs a rigorous 
test. The case for cosmic acceleration rests on the observation that 
SNe Ia at z ~ 0.5 are ~ 0.25 mag fainter than they would be in a 
universe without acceleration. A powerful and straightforward way to 
assess the reliability of the SN Ia measurement and the conceptual 
framework of its interpretation is to look for cosmic deceleration at 
z >= 1. This would be a clear signature of a mixed dark-matter and 
dark-energy universe. Systematic errors in the SN Ia result attributed 
to grey dust or cosmic evolution of the SN Ia peak luminosity would 
not show this change of sign. We have demonstrated proof of this 
concept with a single SN Ia, SN 1997ff at z = 1.7, found and followed 
by HST. The results suggest an early epoch of deceleration, but this 
is too important a conclusion to rest on just one object. Here we 
propose to use HST for observations of six SNe Ia in the range 1.2 <= 
z <= 1.6, that will be discovered as a byproduct from proposed 
Treasury programs for high-latitude ACS surveys. Six objects will 
provide a much firmer foundation for a conclusion that touches on 
important questions of fundamental physics.

NICMOS 9360

Paschen-alpha Imaging of a SIRTF-Selected Nearby Galaxy Sample

We propose to carry out a NICMOS snapshot survey in the Paschen-alpha 
{PAlpha} emission line and H-band of the sample of galaxies being 
observed at 3.5 -- 160 microns as part of SIRTF Nearby Galaxies Survey 
{SINGS} and a related guaranteed time survey of starburst galaxies. 
The PAlpha images, accessible only from HST, will be combined with 
groundbased HAlpha imaging to measure the extinction in the 
star-forming centers of these galaxies, and obtain robust, extinction-
corrected maps of the massive star formation rate {SFR}. The PAlpha 
data by themselves will provide reliable `extinction- free' SFRs, and 
a cross-calibration of the {dust--affected} HAlpha-- and UV--based 
SFRs. The PAlpha--based SFR measurements will extend the SFR-vs.-gas 
density law {Schmidt--law} to surface densities at least 30 times 
higher than what is accessible using HAlpha--based SFR measurements 
alone, bridging the gap between normal galaxies and IR--luminous 
starbursts. Furthermore, the combination of the HST PAlpha images with 
the SIRTF images and spectra, as well as ancillary ground--based 
UBVRIJHK images and GALEX UV images being obtained as part of the
SINGS project, will provide a definitive study of the radiative 
transfer of starlight and dust heating in star--forming galaxies. The 
processed NICMOS images will be incorporated into the public SINGS 
Legacy Data Archive, to enable scores of follow-up studies by the 
astronomical community at large.

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/FUV 9412

The Physical Parameters of the Hottest, Most Luminous Stars as a 
Function of Metallicity

We have obtained excellent, new ground-based blue optical and HAlpha 
spectra of a sample of very early-type stars in the Magellanic Clouds 
in order to measure their physical properties, for comparison with the 
extensive data that exists for higher-metallicity Galactic stars. Our 
aim is to understand how effective temperatures depend upon 
metallicity {necessary in determining IMFs}, and to explore the 
astrophysically interesting regime of stars of extreme temperatures,
masses, and luminosities. In order to do this, we need to measure the 
stellar wind terminal velocities for our stars, necessary to constrain 
the stellar models. These can only be measured with STIS/FUV on HST. 
In addition, we will obtain higher spatial resolution data on the 
HAlpha line for stars for which nebular contamination is significant 
in our ground-based data. We also include several R136 stars with 
excellent STIS/CCD data but which lack UV line measures.  These new 
HST data will provide important information about the strengths of
stellar winds at extreme luminosities and the calibration of the Wind 
Momentum- Luminosity Relationship at lower metallicities. This 
proposal was highly rated in Cycle 9, but only 4 snapshots were 
obtained. We have completed the analysis of these plus additional data 
from the archives, but need spectra of the remaining objects if we are 
to answer the questions we pose.

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