Status Report

NASA Hubble Space Telescope Daily Report # 3391

By SpaceRef Editor
June 25, 2003
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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.


Towards a global understanding of accretion physics –, Clues from an UV
spectroscopic survey of cataclysmic variables

Accretion inflows and outflows are fundamental phenomena in a wide
variety of astrophysical environments, such as Young Stellar Objects,
galactic binaries, and AGN. Observationally, cataclysmic variables
{CVs} are particularly well suited for the study of accretion
processes. We propose to carry out a STIS UV spectroscopic snapshot
survey of CVs that fully exploits the diagnostic potential of these
objects for our understanding of accretion physics. This survey will
provide an homogenous database of accretion disc and wind outflow
spectra covering a wide range of mass transfer rates and binary
inclinations. We will analyze these spectra with state-of-the-art
accretion disc model spectra {SYNDISK}, testing our current knowledge
of the accretion disc structure, and, thereby, providing new insight
into the so far not well understood process of viscous dissipation. We
will use our parameterized wind model PYTHON for the analysis of the
radiation driven accretion disc wind spectra, assessing the
fundamental question whether the mass loss rate correlates with the
disc luminosity. In addition, our survey data will identify a number
of systems in which the white dwarf significantly contributes to the
UV flux, permitting an analysis of the impact of mass accretion on the
evolution of these compact stars. This survey will at least double, if
not triple, the number of high-quality accretion disc / wind outflow /
accreting white dwarf spectra, and we waive our proprietary rights to
permit a timely use of this database.

STIS 9397

Unmasking the optical counterpart to the ultraluminous X-ray source,
NGC 5204 X-1

We propose HST/STIS near- and far-UV spectroscopy of the recently
identified optical counterpart to the ultraluminous X-ray source {ULX}
NGC 5204 X-1 {Roberts et al. 2001}. This source has since been
resolved with HST/WFPC2 {data just public} into two sources with V
magnitudes of 20.5 and 22.0 respectively, separated by 0.4 arcsecs {10
pc at the distance of NGC 5204}. Existing low resolution ground-based
data are dominated by the brighter source, the spectrum of which
appears blue and apparently featureless, consistent with either {i} at
least one unusually bright supergiant O star {M_v<=-7.8}, or {ii} an O
star association, although the data cannot presently rule out the
presence of a background BL-Lac object. Ground-based data cannot
unambiguously type both the new sources, due to their small separation
{there are no bright nearby stars necessary for adaptive optics}, and
the absence of strong features in the optical spectra of O stars. By
observing with the HST/STIS far- and near-UV MAMA we will obtain
spectra in a waveband rich in O star absorption features, with
sufficient S/N {10–15} and resolution {0.6- 1.5Angstrom} to identify
the sources, and reveal the nature of the first optical counterpart to
an ULX. This result will be an important step in determining whether
most ULX systems contain a new, 10^2 – 10^3 M_odot `intermediate-mass’
class of black hole.

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


NICMOS Observations of Transient Infrared Jets in the Galactic
Microquasar GRS1915+105

We propose to use HST/NICMOS to make Target of Opportunity
observations of the galactic microquasar GRS1915+105. This source
possesses transient radio jets which exhibit apparent superluminal
motions, and resolved infrared emission from these jets has been
observed in GRS1915+105 {Sams, Eckart, and Sunyaev, 1996; Eikenberry
and Fazio, 1996}. Because the jet ejection events are correlated with
X-ray outbursts, we will use observations of X-ray flares with the
Rossi X-Ray Timing Explorer to trigger the HST observations. We will
then monitor GRS1915+105 periodically with NICMOS, obtaining relative
astrometry, photometry, polarimetry, and grism spectroscopy of the
jets and the parent object. These observations will allow us to
greatly increase our understanding of the jets’ radiative mechanisms
and physical conditions, and their evolution with time. We require the
capabilities of HST and NICMOS due to the small angular separations
between the jets and the parent object {increasing from ~ 0.1 to ~ 0.8
arcsec over the span of the TOO observations} and the high reddening
towards GRS1915+105 {A_V ~ 30 mag}.

WFPC2 9595


This dark calibration program obtains 3 dark frames every day to
provide data for monitoring and characterizing the evolution of hot

STIS 9606

CCD Dark Monitor-Part 2

Monitor the darks for the STIS CCD.

STIS 9608

CCD Bias Monitor – Part 2

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

STIS 9627

CCD Sensitivity Monitor for Cycle 11

Monitor sensitivity of each CCD grating mode to detect any change due
to contamination or other causes. Also monitor the STIS focus in an
imaging mode

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.

ACS 9658

ACS Earth Flats

This program will obtain sequences of flat field images by observing
the bright Earth. Several UV filters from the interim calibration
program {9564} require additional exposures to obtain the required
illumination. A few UV filters from this program will be repeated to
monitor for changes in the flat fields and to verify the interim
results. Since no streaks are observed in the UV, the wavelength
coverage is extended to longer wavelengths in order to explore the
severity of streaks in the flats from clouds in the FOV. We have added
exposures for the HRC in the visible filters to verify the results
derived from the L-flat campaign and to explore the severity of
streaks. We have also added exposures on WFC using the minimum
exposure time and using filters which will not saturate the brightest
WFC pixel by more than 10 times the full well.

ACS 9674

CCD Daily Monitor

This program consists of basic tests to monitor, the read noise, the
development of hot pixels and test for any source of noise in ACS CCD
detectors. This programme will be executed once a day for the entire
lifetime of ACS.

WFPC2 9709

POMS Test Proposal: WFII parallel archive proposal

This is the generic target version of the WFPC2 Archival Pure Parallel
program. The program will be used to take parallel images of random
areas of the sky, following the recommendations of the 2002 Parallels
Working Group.

STIS 9783

The Ages of Nuclear Star Clusters in Early-type Spiral Galaxies

We propose to obtain STIS G430L spectra of the previously identified
nuclear star cluster in a sample of 16 spiral galaxies of early to
intermediate Hubble type. HST’s spatial resolution is required to
separate the nuclear cluster from the underlying galaxy bulge.
Analysis of the spectra with population synthesis methods will reveal
the cluster ages. We will use the age distribution to constrain the
duty cycle of nuclear cluster formation. Comparison of the results to
those for a larger sample of nuclear clusters in late-type, bulgeless
galaxies will allow us to investigate possible differences between the
formation mechanisms of nuclear clusters in early and late Hubble
types. Such differences might be expected because galaxy bulges show a
dichotomy: in late Hubble types, the surface brightness profiles are
best described by an exponential, while they follow a de Vaucouleurs
law in earlier types. Although the reason for this dichotomy is still
unknown, it is plausible that galaxy bulges have different formation
mechanisms at the two ends of the Hubble sequence. We know that {1}
nuclear cluster formation is linked to the funneling of gas towards
the nucleus via gravitational torques from stellar bars, {2} a nuclear
mass concentration can make bars unstable, and {3} unstable bars can
form bulges. Therefore, the age distribution of nuclear star clusters
contains important clues to the evolution of galaxy centers and
promises new insight into the origin of the Hubble sequence.

ACS 9984

Cosmic Shear With ACS Pure Parallels

Small distortions in the shapes of background galaxies by foreground
mass provide a powerful method of directly measuring the amount and
distribution of dark matter. Several groups have recently detected
this weak lensing by large-scale structure, also called cosmic shear.
The high resolution and sensitivity of HST/ACS provide a unique
opportunity to measure cosmic shear accurately on small scales. Using
260 parallel orbits in Sloan textiti {F775W} we will measure for the
first time: beginlistosetlength sep0cm setlengthemsep0cm setlength
opsep0cm em the cosmic shear variance on scales <0.7 arcmin, em the
skewness of the shear distribution, and em the magnification effect.
endlist Our measurements will determine the amplitude of the mass
power spectrum sigma_8Omega_m^0.5, with signal-to-noise {s/n} ~ 20,
and the mass density Omega_m with s/n=4. They will be done at small
angular scales where non-linear effects dominate the power spectrum,
providing a test of the gravitational instability paradigm for
structure formation. Measurements on these scales are not possible
from the ground, because of the systematic effects induced by PSF
smearing from seeing. Having many independent lines of sight reduces
the uncertainty due to cosmic variance, making parallel observations


Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.) None



                           SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq               9                          9
FGS REacq               5                          5
FHST Update             23                         23


SpaceRef staff editor.