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12 May 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT        # 3360

PERIOD COVERED: DOYs 129-131

Part 4 of 5

SNAP/STIS 9434

A SNAPSHOT Survey of the Hot Interstellar Medium

We propose to obtain SNAPSHOT STIS echelle observations of key
tracers of hot interstellar gas {CIV, NV and SiIV} for selected FUSE
Team OVI survey targets with known UV fluxes. By taking advantage of
the SNAPSHOT observing mode we will efficiently obtain a large number
of spectra suitable for the study of the highly ionized hot component
of the interstellar medium {ISM}. Our goals are to explore the
physical conditions in and distribution of such gas, as well as to
explore the nature of the interfaces between the hot ISM and the
other interstellar gas phases. Using inter--comparisons of the
various ionic ratios for CIV, NV, OVI and SiIV, we will be able to
discriminate between the various models for the production of the
highly ionized gas in the Galactic ISM. The survey will also enable
detailed studies of regions already known to contain hot gas through
X-ray emission measurements {e.g., SNRs and radio loops}. The
proposed SNAPSHOT observations will extend our previous Cycle 9
survey {which was compromised by the STIS side 1 failure}, and should
roughly double the number of stars for which high quality STIS
observations of the important hot gas tracers are available, enabling
us to derive a truly global view of the hot ISM.

STIS 9608

CCD Bias Monitor - Part 2

Monitor the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at
gain=1, and 1x1 at gain = 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 9631

Faint Standard Extension {FASTEX}

Fainter standard stars are needed for the flux calibration of COS,
for the prism modes on ACS, and for astronomical community, in
general. The bright object safety limit for COS is 1.25 ct/s per
pixel, while the total countrate limit per FUV detector segment is
20000/s. In addition, the GALEX project {see Appendix} requires more
secondary standards in the flux range of the two fainter original
FASTEX stars. Customarily, one NASA project provides observing time
in support of other NASA projects. The existing observations of the
two fainter FASTEX standards, WD0947+857 and WD1657+343, have the
most CTE losses in the G430L data and are still a bit marginal on
S/N. Since the stellar models are normalized to V, good
spectrophotometry to 5500A is important. All five targets will be
observed at the new G430L aperture to minimize CTE loss and at the
original aperture to constrain CTE models. Combined with additional
planned cal data for stars of intermediate flux, the CTE model for
spectra can be tuned to cover the full range of signal levels.

STIS 9339

Physical Parameters of the Erupting Luminous Blue Variable NGC
2363-V1

In 1996, we reported the discovery of a bright variable star in the
giant extragalactic H , ii region NGC 2363. Subsequent photometry and
high quality HST/STIS spectroscopy of this star, NGC 2363-V1,
revealed that we are witnessing a significant event in the evolution
of a massive star, namely a major eruption of a Luminous Blue
Variable {LBV}. A quantitative analysis of the STIS datasets gathered
in 1997 and 1999 allowed us to determine the luminosity, mass loss
rate, wind terminal velocity, surface temperature and even Fe content
of this erupting LBV. Because such events are rare, continuous
monitoring of the physical parameters of NGC 2363- V1 over the course
of its present eruption will provide an invaluable set of constraints
for theoretical models. We therefore propose to obtain high quality
STIS spectra of this star once a year for the next three observing
Cycles. 

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/ACS 9384

Ozone, Condensates, and Dust in the Martian Atmosphere

We propose to utilize the unique UV capabilities of STIS and ACS/HRC
in order to study the spatial and seasonal variations in ozone,
condensates, and dust in the Martian atmosphere. The data obtained
will be critical in addressing recent breakthroughs in understanding
the basic radiative, transport, and microphysical processes that
provide for both long-term and short-term balance within the global
Mars climate system. The proposal includes both Cycle 11 & 12
observations in order to span the classic dust storm season on Mars
and provide the first good opportunity for HST to synoptically
observe a dusty atmosphere on the planet. The UV observations will
complement broad-band visible and IR observations that will be made
during the Mars Global Surveyor Extended Mission and will provide
support for the future UV observations of MARCI on the 2005 Mars
Reconnaissance Orbiter. 

 - Continued -

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