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HUBBLE SPACE TELESCOPE

DAILY REPORT        # 3155

PERIOD COVERED: DOYs 122-124

Part 4 of 5

SNAP 9356

SNAPSHOT survey of the Planetary Nebulae population of the Galactic
Bulge 

The spectacular structures seen in HST images of planetary nebulae
{PNe} are generally accepted as originating from hydrodynamical
interactions between stellar winds: the interacting-stellar wind
model {ISW}. Traditionally, the shaping is thought to occur after the
star becomes hot enough to ionize the PN. But recent HST images
indicate that the shaping may occur earlier, and the newer GISW model
puts the shaping during the pre-planetary nebula evolution. The
relative importance of both models is not known: GISW shaping will
account for some fraction of PNe, but estimates range from 15--100
during the PN phase, especially for the youngest PNe. We here propose
an HST Snapshot survey of compact PNe in the Galactic Bulge, to test
these predictions. The Bulge provides the only PNe population for
which progenitor masses are known and nebular ages can be measured.
In support of these HST measurements we have already measured
velocity fields and emission line fluxes. The survey will give an
unbiased sampling of morphologies, and allow evolutionary sequences
to be determined to test the ISW versus the GISW model. By-products
of the survey will be the determination of nebular masses, diameters
and filling factors. We will also obtain the White Dwarf mass
distribution in the Bulge, and the initial-final mass function for
low-mass stars. 

STIS 9608

CCD Bias Monitor - Part 2

Monitor the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at
gain= 3D1, and 1x1 at gain =3D 4, to build up high-S/N superbiases
and track the evolution of hot columns.

STIS 9606

CCD Dark Monitor-Part 2

Monitor the darks for the STIS CCD.

STIS 9447

Characterizing the Atmosphere of an Extrasolar Planet

HD 209458 b is the first extrasolar planet known to transit the disk
of its parent star. Precise measurement of both the photometric
transit curve and the radial velocity orbit has allowed for an
accurate estimation of the mass, radius, average density, and surface
gravity. Numerous theoretical investigations of the planetary
atmospheres have been presented in the literature, but no data
capable of addressing these has yet been published. We propose to use
the method of transmission spectroscopy to constrain greatly models
of the planetary atmosphere. We will use STIS to disperse the stellar
flux over a large number of detector pixels. The photometric signal
is produced by summing the counts over a desired band. For each of
twelve bands spanning the UV to the near-IR, we will obtain
sufficient precision to detect variations in the transit depth
greater than 5 X 10^-5. We have already made a detection of the
sodium absorption signature in the planetary atmosphere. With these
new data, we will be able to detect, if present, absorption due to
Rayleigh scattering, water bands, and/or strong alkali metal lines.
These observations will allow us to determine the broad
characteristics of the planetary atmosphere. For example, we will be
able to distinguish between models with a high cloud deck, and those
with no clouds but reduced chemical abundances. 

STIS 9633

STIS parallel archive proposal - Nearby Galaxies - Imaging and
Spectroscopy

Using parallel opportunities with STIS which were not allocated by
the TAC, we propose to obtain deep STIS imagery with both the Clear
{50CCD} and Long-Pass {F28X50LP} filters in order to make
color-magnitude diagrams and luminosity functions for nearby
galaxies. For local group galaxies, we also include G750L slitless
spectroscopy to search for e.g., Carbon stars, late M giants and
S-type stars. This survey will be useful to study the star formation
histories, chemical evolution, and distances to these galaxies. These
data will be placed immediately into the Hubble Data Archive.

STIS 9708

STIS Pure Parallel Imaging Program: Cycle 11

This is the default archival pure parallel program for STIS during
cycle 11.

STIS 9441

Zinc Abundances in Damped Ly-Alpha Systems at z < 0.5: A Missing Link
in the Chemical History of Galaxies

The evolution of metallicity in damped Lyman alpha {DLA} quasar
absorption systems is an important constraint on the global star
formation history of the universe, but remains a big puzzle at
present. The H I column density weighted mean metallicity in DLAs is
expected to rise to solar values at low redshifts, based on cosmic
chemical evolution models, because the mass-weighted mean metallicity
of local galaxies is near- solar. However, current DLA abundance
studies are highly uncertain and cannot distinguish between evolution
and no evolution in the mean metallicity at redshifts 0.4 < z < 3.5.
The existing data are particularly incomplete because no Zn
measurements exist for z < 0.4, and only 2 exist for z < 0.5, which
spans the past 35-45 % of the age of the universe. To pin down the
cosmic age-metallicity relation all the way to the present epoch, we
propose to measure Zn abundances in five DLAs at 0.1 < z < 0.5. We
propose to use HST STIS because it is the only existing instrument
that can measure the necessary UV lines. Our observations will
clearly distinguish between no metallicity evolution vs. the
predicted evolution. Our data will also provide Cr measurements,
which will help to estimate the dust abundance. The proposed
observations are crucial for tying together the absorption and
emission histories of gas and stars in galaxies and for clarifying
the relation of DLAs to present-day galaxies. 

STIS/CAL 9628

MAMA Sensitivity and Focus Monitor Cycle 11

Monitor sensitivity of each MAMA grating mode to detect any change
due to contamination or other causes. Also monitor the STIS focus in
a spectroscopic and imaging mode.

 - Continued -

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