Status Report

NASA Hubble Space Telescope Daily Report # 3501

By SpaceRef Editor
December 8, 2003
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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 10050

ACS Earth Flats

High signal sky flats will be obtained by observing the bright Earth
with the HRC and WFC. These observations will be used to verify the
accuracy of the flats currently used by the pipeline and will provide
a comparison with flats derived via other techniques: L-flats from
stellar observations, sky flats from stacked GO observations, and
internal flats using the calibration lamps. Weekly coronographic
monitoring is required to assess the changing position of the spots.

ACS/HRC 9422

Masses of AGB stars

There are few AGB stars with known masses. We have undertaken a
program to measure spectroscopic orbits for about 50 binary systems
containing M giants and typically white dwarfs. These are all single
lined systems so the spectroscopic orbit of the M giant results in a
mass function, m_2^3sin^3i / {m_1 + m_2}^2, for the secondary. Under
special conditions, it is possible to undertake a simple observation
that allows a solution for the masses. By measuring the angular
separation at the epoch of greatest elongation of a zero eccentricity,
eclipsing system {i.e. a system with a known inclination} m_1+m_2 can
be determined, hence allowing the masses to be solved. Parallaxes
indicate that there are two systems that can be resolved using
HST/ACS. We propose to carry out this observation.


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.


The Grism-ACS Program for Extragalactic Science {GRAPES}

We propose an ACS grism spectroscopic survey with a wide component and
an ultradeep single ACS field. The wide component covers the
well-imaged GOODS Chandra Deep Field south and the deepest field will
be the Ultra Deep field to be observed in cycles 11 and 12. The Grism
ACS Program for Extra-galactic Science {GRAPES} will: {1} Probe the
reionization epoch by robustly determining the luminosity function of
Lyman-alpha emitters, Lyman break galaxies and low luminosity AGNs at
z~6, and thus the sources of ionizing photons at the end of the "dark
ages". A similar census of ionizing photon sources at z=4-6 needed to
maintain the ionized state of the IGM will also be achieved. {2} Study
galaxy formation and evolution by finding galaxies in a contiguous
redshift range between z=4-7 and evolution of black holes through a
census of low-luminosity AGNs. {3} Study star-formation and galaxy
assembly at its peak at z=1-2 by identifying star-forming galaxies by
their emission lines, old galaxies by the 4000 AA break and any
combination of new and old populations showing both lines and breaks.
{4} Allow the deepest unbiased spectroscopy yet, for identification of
objects to I=27. {5} Enhance the value of multiwavelength data in the
UDF and GOODS field to the astronomical community.

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


The Role of Groups in the Evolution of Galaxies at Intermediate

Groups are the most common environment experienced by galaxies, yet
they remain the least studied. The tidal fields and dynamical friction
encountered by galaxies in groups probably holds the key to
understanding the role of environment in driving the evolution of
galaxies since z ~ 1. To study the evolution of galaxies in the group
environment, we propose the first unbiased HST study of groups at
moderate redshifts. Unlike previous HST group samples, that relied on
radio or X-ray properties, our kinematically selected sample is drawn
from a large redshift survey and is not biased towards unusually dense
groups. HST imaging is essential to determine the morphology of
galaxies in these systems and contrast this with the properties of
galaxies in denser and more evolved groups and rich clusters at these
epochs. HST data are also required to adequately compare the
properties of groups at intermediate redshifts with local group
samples derived from the 2df and Sloan surveys. We will combine the
HST images with deep ground-based observations to study how
morphologies and stellar populations of galaxies in groups have
evolved in time. These observations are key to understanding the
decline in the volume averaged star formation rate in the universe.

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.

STIS 9633

STIS parallel archive proposal – Nearby Galaxies – Imaging and

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/CCD 10000

STIS Pure Parallel Imaging Program: Cycle 12

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

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.


A SNAPSHOT Survey of Sharp-Lined Early B-Type Stars

Although spectrum synthesis studies of the UV spectra of sharp-lined
main sequence B stars provide us with some our best determinations of
the abundances of the Fe group and neutron capture elements and the
chemical evolution in our galaxy and the Magellanic Clouds, the HST
archive is virtually devoid of high resolution spectra of the bright
nearby B stars that have become to be regarded as abundance standards.
For example, there are NO observations of HR 1886, iota Her, and tau
Her, the sharpest-lined representatives {V sin i < 5 km/s} of spectral
classes B1 V, B3 IV-V and B5 IV, and only a few tiny spectral
intervals of gamma Peg {B2 IV}. Information on the abundances of the
Fe group is important for computing opacities for stellar evolution
calculations and for determining astrophysical f-values. There are no
suitable galactic standards in the HST database to compare with recent
HST/STIS observations of B stars in the Magellanic Clouds and the
likely future observations of similar objects in M31 and other nearby
galaxies. To correct this deficiency, we propose SNAPSHOT observations
with the STIS E140M and E230M gratings of 33 of the best bright
abundance standards in nearby clusters and the galactic field. Using
this data we will determine the abundances of the Fe group and heavy
elements using the technique of spectrum synthesis with LTE and NLTE
treatments. We waive the proprietary period.


The Physical Parameters and Stellar Winds of Hot, Massive Stars at
High Metallicity: O-stars in the Andromeda Galaxy

Stellar winds are a ubiquitous phenomenon among high luminosity hot
stars, and the resulting mass-loss has a significant effect on their
evolution, as a very massive star might lose half its mass during its
main-sequence life. There has been significant progress in
understanding the physics of radiatively-driven winds, and simple
theoretical parameterizations of mass-loss with stellar properties,
such as luminosity, effective temperature, and surface gravity, have
been developed. These provide good agreement with the observed
mass-loss rates for Galactic stars. Scaling these mass-loss rates to
other environments, where the metallicity Z is different than solar,
requires a power-law in Z, but various studies have found values for
this exponent ranging from 0.5 to 1.0. Here we are hampered by the
scant range in metallicities covered by the observational database,
which extends only from one-third solar {SMC} to solar {Milky Way}. We
are proposing to extend this work to a sample of four O8-O8.5If stars
in the Andromeda Galaxy {M31}, where the metallicity measured from HII
regions is about twice solar. Significant ground-based and HST time
has gone into setting the stage for this, but it is only in the last
few years that good throughput in the FUV {thanks to STIS/MAMA} and
large aperture optical telescopes have permitted the gathering of data
of the quality needed for a quantitative spectroscopic analysis
similar to what we can do for low-metallicity Magellanic Cloud stars.
We have obtained most of the optical spectra we need with the newly
refurbished 6.5-m MMT and are now requesting the FUV spectra that only
HST/STIS can provide. The resulting analysis will not only yield
mass-loss rates but also the physical parameters {Teff, log g,
luminosity, radius, mass, and metallicity}, which can then be compared
to their lower-metallicity counterparts. Parallel imaging with WFPC2
and ACS will provide data useful to ourselves and others for the study
of the resolved stellar population of the Local Group galaxy most like
our own.

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 10073

Earth Flats

This proposal monitors flatfield stability. This proposal obtains
sequences of Earth streak flats to construct high quality flat fields
for the WFPC2 filter set. These flat fields will allow mapping of the
OTA illumination pattern and will be used in conjunction with previous
internal and external flats to generate new pipeline superflats. These
Earth flats will complement the Earth flat data obtained during cycles

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 9712

Pure Parallel Near-UV Observations with WFPC2 within High-Latitude ACS
Survey Fields

In anticipation of the allocation of ACS high-latitude imaging
survey{s}, we request a modification of the default pure parallel
program for those WFPC2 parallels that fall within the ACS survey
field. Rather than duplicate the red bands which will be done much
better with ACS, we propose to observe in the near-ultraviolet F300W
filter. These data will enable study of the rest-frame ultraviolet
morphology of galaxies at 0<z<1. We will determine the morphological
k-correction, and the location of star formation within galaxies,
using a sample that is likely to be nearly complete with
multi-wavelength photometry and spectroscopic redshifts. The results
can be used to interpret observations of higher redshift galaxies by


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



                          SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq              10                       10
FGS REacq              5                         5
FHST Update            21                       21


SpaceRef staff editor.