Status Report

NASA Hubble Space Telescope Daily Report # 3520

By SpaceRef Editor
January 1, 2004
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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

ACS/HRC 9812

Ultraviolet Emission from Protostellar Accretion Disks

We propose to obtain ACS/prism observations of the UV continuum
emitted by protostellar accretion disks. By combining the ACS data
with simultaneous ground-based optical spectra and near-IR photometry,
we will be able to observe the entire spectral energy distribution of
the young stars and their disks from 1800A to 3.5um. The combined data
set will solve the long-standing problem of degeneracy between
reddening, spectral type, and excess emission in the analysis of such
spectra by allowing us to measure reddenings directly from the 2175A
bump, bolometric corrections from the UV continuum, and effective
temperatures from the optical spectra. With this information in hand
it will be possible for the first time to quantify the mass accretion
rates, stellar radii, masses, and ages without the systematic
uncertainties that have plagued previous efforts. The new data will
probe the physical conditions that exist where material from the disk
falls onto the star, such as filling factors, temperatures, and
optical depths. We will also be able to place heavily veiled stars
unambiguously in HR diagram for first time to see if these stars are
on average younger than their more slowly accreting counterparts, and
test whether or not the Mg II 2800A doublet traces jets close to their
stars. The proposed observations will yield the first simultaneous
coverage over all the principal wavelengths that these accretion disks
emit; a true multiwavelength approach is the only way to clarify what
goes on in accretion/outflow systems, a process common throughout


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.


Observations of Intermediate Mass Black Hole Candidate Ultra-Luminous
X-ray Sources

Ultra-luminous X-ray {ULX} sources are off-nuclear point sources in
nearby normal galaxies. Variability observed on the timescale of days,
weeks, and years signals that ULXS are accreting sources, likely
harboring black holes. However, the observed X-ray luminosity of these
systems far exceeds the Eddington limit for a 10 Msun black hole; some
ULXs may be intermediate mass black holes. The identification and
study of optical counterparts with HST will be central to better
understanding these objects. We propose to obtain deep U-B-V-I
exposures of 4 extremely bright ULXs in nearby spirals: NGC 1313 X-1
and X-2, M81 X-9 {Holmberg II X-1}, and M74 X-1. Each has a 0.5”
Chandra position, and X-ray luminosity and spectral characteristics
consistent with expectations for intermediate mass black holes. We
will use the colors we obtain, the magnitudes we measure, and any
source variability {also, correlated optical-X-ray variability from
simultaneous Chandra snapshots} to constrain the nature of the donor
stars and the black holes {10 Msun or 100-1000 Msun}, and the
formation and evolution scenarios for each system.

ACS/WFC 9860

ESSENCE: Measuring the Dark Energy Equation of State

The accelerating universe appears to be dominated by a dark energy
with a significant negative pressure. The ratio of the pressure to
density of this mysterious energy {its equation of state} is an
observable which can differentiate between the proliferating candidate
theories. We propose to estimate the dark energy equation of state by
observing Type Ia supernovae at redshifts near z=0.7 with HST in
concert with the on-going ESSENCE NOAO Survey program that is
discovering and studying supernovae between 0.3<z<0.8. We show that an
interesting constraint on the equation of state can be made with
supernovae observed at modest redshifts given the current knowledge of
the matter density. We will follow 10 Type Ia supernovae discovered
from the ground and passed to HST without disrupting its schedule. The
full data set will constrain the equation of state to 10% and strictly
limit the range of possible dark energy models. In keeping with the
ESSENCE policy, these observations will available to the community

ACS/WFC 9892

H-alpha Snapshots of Nearby Galaxies observed in F300W: Quantifying
Star Formation in a Dusty Universe

Previous studies of nearby galaxies show large discrepancies between
different star formation {SF} indicators on large {>100 pc, or even
global} scales: the strikingly complex interplay of young stars, dust
and ionized gas are the primary cause of this variance. The few
galaxies in the HST Archive with both WFPC2 H-alpha and mid-UV {F255W
or F300W} imaging show this complex geometry extending down to <10 pc
scales. We propose a SNAPshot survey in the ACS/WFC H-alpha filter of
48 galaxies of all Hubble types, that are nearby but beyond the Local
Group, and that were previously imaged with WFPC2 in the mid-UV and in
F814W. We aim to provide a benchmark for understanding the SF
processes in both normal and star-bursting galaxies, at spatial
resolutions unattainable from the ground for a large and varied galaxy
sample. These data can be applied to a wide range of astrophysical
problems and will, therefore, be made public immediately. Our science
goals are to: {1} spatially resolve the dust clouds and filaments
which strongly affect mid-UV and H-alpha derived SF rates, {2} test
how the large-scale correlation between H-alpha and mid-UV flux breaks
down on pc scales, and {3} model the propagation of star formation by
comparing the SF over time scales of ~100 Myr {via mid-UV} and ~5 Myr
{via H-alpha}. This will {4} significantly improve our insight into,
and calibration of SF in UV-bright galaxies at high z, and into the
cosmic SF history.


Calibration of the ACS Emission Line Filters

The emission line filter set for the ACS is seriously compromised
because the Halpha and the primary [N II] lines are transmitted
equally well by the F658N filter. This prevents an absolute
calibration of these images with only a single filter, because one
doesn’t know the intrinsic ratio of these two lines. Absolute
calibration is possible if one also makes observations in the [N II]
dominated F660N filter and the calibration constants are known. This
proposal describes a program that will allow determination of the
calibration constants for the three emission line filters and how the
observations can be corrected for continuum radiation passed through
the same filters. The method was developed originally for WFPC2 and
successfully applied there. The well calibrated Orion Nebula will be
used as a reference source. Coordinate parallel observations of
previously unobserved regions of the Orion Nebula and M 43 will be
possible and these will be used to continue discovery of proplyds and
other phenomena related to young stellar objects.

FGS 10010

Long Term Monitoring of FGS1r in Position Mode

It is known from our experience with FGS3, and later with FGS1r, that
an FGS on orbit experiences long term evolution, presumably due to
disorption of water from the instrument’s graphite epoxy composites.
This manifests principally as a change in the plate scale and
secondarily as a change in the geometric distortions. These effects
are well modeled by adjustments to the rhoA and kA parameters which
are used to transform the star selector servo angles into FGS {x, y}
detector space coordinates. By observing the relative positions of
selected stars in a standard cluster at a fixed telescope pointing and
orientation, the evolution of rhoA and kA can be monitored and
calibrated to preserve the astrometric performance of FGS1r.

NIC/NIC3 9865

The NICMOS Parallel Observing Program

We propose to continue managing the NICMOS pure parallel program.
Based on our experience, we are well prepared to make optimal use of
the parallel opportunities. The improved sensitivity and efficiency of
our observations will substantially increase the number of
line-emitting galaxies detected. As our previous work has
demonstrated, the most frequently detected line is Halpha at
0.7<z<1.9, which provides an excellent measure of current star
formation rate. We will also detect star-forming and active galaxies
in other redshift ranges using other emission lines. The grism
observations will produce by far the best available Halpha luminosity
functions over the crucial–but poorly observed–redshift range where
galaxies appear to have assembled most of their stellar mass. This key
process of galaxy evolution needs to be studied with IR data; we found
that observations at shorter wavelengths appear to have missed a large
fraction of the star-formation in galaxies, due to dust reddening. We
will also obtain deep F110W and F160W images, to examine the space
densities and morphologies of faint red galaxies. In addition to
carrying out the public parallels, we will make the fully reduced and
calibrated images and spectra available on-line, with some
ground-based data for the deepest parallel fields included.


NICMOS Post-SAA calibration – CR Persistence Part 1.

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 Origin of Gamma-Ray Bursts

The rapid and accurate localization of gamma-ray bursts {GRBs}
promised by a working HETE-2 during the coming year may well
revolutionize our ability to study these enigmatic, highly luminous
transients. We propose a program of HST and Chandra observations to
capitalize on this extraordinary opportunity. We will perform some of
the most stringent tests yet of the standard model, in which GRBs
represent collimated relativistic outflows from collapsing massive
stars. NICMOS imaging and STIS CCD spectroscopy will detect broad
atomic features of supernovae underlying GRB optical transients, at
luminosities more than three times fainter than SN 1998bw. UV,
optical, and X-ray spectroscopy will be used to study the local ISM
around the GRB. Chandra spectroscopy will investigate whether the GRB
X-ray lines are from metals freshly ripped from the stellar core by
the GRB. HST and CTIO infra-red imaging of the GRBs and their hosts
will be used to determine whether `dark’ bursts are the product of
unusually strong local extinction; imaging studies may for the first
time locate the hosts of `short’ GRBs. Our early polarimetry and
late-time broadband imaging will further test physical models of the
relativistic blast wave that produces the bright GRB afterglow, and
will provide unique insight into the influence of the GRB environment
on the afterglow.

STIS/CCD 10017

CCD Dark Monitor-Part 1

Monitor the darks for the STIS CCD.

STIS/CCD 10019

CCD Bias Monitor – Part 1

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/CCD 10085

STIS Pure Parallel Imaging Program: Cycle 12

This is the default archival pure parallel program for STIS during
cycle 12.

STIS/MA1 10034

Cycle 12 MAMA Dark Monitor

This test performs the routine monitoring of the MAMA detector dark
noise. This proposal will provide the primary means of checking on
health of the MAMA detectors systems through frequent monitoring of
the background count rate. The purpose is to look for evidence of
change in dark indicative of detector problem developing.

WFPC2 10069

WFPC2 CYCLE 12 Supplemental Darks, Part 1/3

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

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.

WFPC2 9968

Fundamental properties of L-type dwarfs in binaries

We propose to characterize the physical properties of eight L-dwarfs
in four binary systems. Our goal is to obtain astrometric, photometric
and spectroscopic measurements of each component that will yield basic
information on their atmospheric and dynamical properties. The high
angular resolution of HST is essential because all these systems have
angular separations $le$0.5 arcsec. They do not have bright enough
stars nearby that can be used for natural guide adaptive optics in
ground-based telescopes. In Cycles~10 and 11 we propose to obtain
WFPC2 and STIS data, allowing the determination of parallax, proper
motion, position and spectral type for each component. In Cycle 12 we
plan to obtain additional WFPC2 images for follow-up of the orbital
motion and refinement of parallax and proper motion. We will also
monitor possible intrinsic photometric variability in two filters
{F675W and F814W}. The STIS observations will provide spectral types,
gravity sensitive indicators, and chromospheric activity {H$_ lpha$
emission} for each component. These 4 systems will constitute
benchmarks for determining dynamical masses of L dwarfs, and inferring
the age-mass-spectral type relationship of this new spectral class.


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

17074-0 – Genslew for proposal 9862, slot 12 @ 363/2136z
17075-0 – Genslew required for proposal 9862, slot 13 @ 363/2137z
17076-0 – Genslew required for proposal 9703, slot 14 @ 363/2138z


                            SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq                11                        11
FGS REacq                5                          5
FHST Update              24                        24


SpaceRef staff editor.