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4 Apr 2003

HUBBLE SPACE TELESCOPE

DAILY REPORT        # 3334

PERIOD COVERED: DOY 93

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.

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. 

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.

ACS 9454

The Nature of the UV Continuum in LINERs: A Variability Test

LINERs may be the most common AGNs, and the signposts of accretion
onto the massive black holes present in most galaxies. However, the
LINER spectrum is the result of UV excitation, and, in at least some
LINERs, a nuclear cluster of hot stars, rather than an AGN, dominates
the energetics in the UV. Thus, it is still unknown if the UV
continuum, or the optical emission lines it excites, have anything to
do with an AGN. The demographics and accretion physics of
low-luminosity AGNs hinge on this question. We propose to search for
variability in a sample of 17 LINERs with compact UV nuclei.
Variability can reveal an AGN component in the UV continuum, even
when its light is not dominant. We will test systematically the
handful of non-definitive reports of UV variability, and potentially
quantify the AGN contribution to the UV emission. Variability in all
or most objects will be strong evidence that LINERs mark dormant AGNs
in most galaxies. Alternatively, a general null detection of
variability will suggest that, even in LINERs with additional AGN
signatures, the UV continuum is stellar in origin. Contemporaneous
monitoring with the VLA/VLBA of 11 objects which have radio cores
{five of which we already know are radio-variable} will reveal the
relations between UV and radio variations. The UV-variable objects
will be targeted for future, better-sampled, monitoring. 

 - Continued -

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