Status Report

NASA Hubble Space Telescope Daily Report # 3537

By SpaceRef Editor
January 23, 2004
Filed under , ,

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science




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
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 ideal.


CCD Daily Monitor

This program consists of basic tests to monitor, the read noise, the
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 role of dark matter and intracluster gas in galaxy formation and cluster

We propose a fully-sampled mosaic of 41 ACS images to survey galaxy
and measure weak lensing signals to the turn-around radius in the X-ray
cluster, MS0451-03 {z=0.54}. The aim is to isolate the physical processes which
affect the evolution of cluster galaxy morphologies in the context of
well-defined dynamical system. The study will be used in contrast to a
successful campaign undertaken in Cycle 9 on a optically-selected target. By
comparing morphologies with spectroscopic and Chandra X-ray data, we will
quantify the role of the intracluster medium and associated substructures and
establish the timescales and physical regions within which the various
environmental processes occur.


Gravitational Microlensing in the NGC 3314A-B Galaxy Pair

Determining the composition of the dark matter that dominates the masses of
galaxies is an important unsolved problem, and the results of the MACHO
Collaboration suggest that some of Milky Way’s dark matter may be in the
form of
very old white dwarfs. However, some have argued that the excess of
events seen by MACHO are due to a larger than expected microlensing rate for
lens stars in the LMC itself or its tidal debris. We propose to address this
question by detecting microlensing events in the line-of-sight galaxy pair NGC
3314 A & B. The large line-of-sight distance between these galaxies gives an
optical depth that is 3-4 orders of magnitude larger than if the source stars
and lenses were in the same galaxy, and the fact that the background galaxy
is a
spiral ensures that there will be a sufficient number of bright, non-variable
source stars. Our proposed observations should have the sensitivity to detect
microlensing by both ordinary stars and dark matter in NGC 3314A {the
galaxy}. If there are dark matter microlensing events to be found, they can be
clearly distinguished from stellar microlensing events because they will occur
outside the visible disk of NGC 3314A. If baryonic dark matter is detected in
NGC 3314A, we will be able to map its radial density variation.


An ACS/WFC H-alpha Survey of the Orion Nebula

We propose to survey nearly 500 square arcminutes of the Orion Nebula in
using the ACS/WFC, increasing the sky coverage by an order of magnitude
over the
sum of all previous HST observations. This survey will, for the first time,
sample the majority of young stars and circumstellar environments in the
extended Trapezium cluster of 2, 000 low-mass stars. Our primary goal is to
determine the survival rate and statistical properties of protoplanetary disks
in the type of radiation field and dynamical environment in which most
stars are
born. The survey will be used to search for new silhouette disks, bright
proplyds, microjets, large-scale outflows, and to characterize the
properties of
these objects as a function of location in the nebula. We will determine
accurate proper motions in regions where previous HST data exist. However, 90%
of our fields will be observed with HST for the first time. This survey will
provide the first complete census of pre-main sequence objects and outflows in
an HII region and will constrain the extent of hazards to planet formation in
such environments. The images will also provide a legacy for future stellar and
nebular variability studies and proper motion measurements by providing a first
epoch data base.

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
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

NIC3 10014

Spectrophotometry of FAINT IR STANDARDS

Faint spectrophotometric standard stars required for COS and the SBC channel on
ACS have been established via the STIS FASTEX program that has executed
over the
last three cycles. Cycle 12 is an especially opportune time to establish
companion faint IR standards for WFC3, because the NICMOS proposal 9998
observations in cycle 12 of all 6 of the primary standard stars in order to
establish the absolute flux calibration of the three grism modes to 1%. In
addition to WFC3, these new faint secondary IR standards will be a significant
step towards establishing flux standards for JWST, as well as for SNAP, SIRTF,
and SOFIA. The 6 primary standards included in Propid=9998 are in the range of
V=11-13 and include three hot pure hydrogen WDs and 3 solar analogs. We propose
to establish new IR faint standards in the 15-17 mag range. Appropriate
types for faint IR standards are solar analogs and hotter WDs. Many M type and
cooler stars are variable, so that long term monitoring is required before
committing HST time to such cool stars. A few G type and WD faint stars will
provide a set of faint IR standards with minimal sky and color coverage.
Existing HST images of any candidates can provide verification that there
are no
contaminating stars above the 1% level within 2-3arcsec. However, the ACS
calibration field in 47 Tuc is too crowded for linking to ground based
observations. If the other candidates are selected from SDSS or other ground
based data, then the NICMOS and STIS acquisition images can provide this
verification, as well as correction factors for arbitrary photometric size
apertures. The SNAP team is providing the northern faint stars using unreleased
SDSS data. In addition, the extreme coolest types such as L and T stars have
proven essential to sorting out the long wavelength QE of ACS; both the ACS and
eventually WFC3 calibrations could be improved with knowledge of L and T
SEDs in
the region beyond 0.95 microns. In addition to the primary purpose of ACS
QE vs.
wavelength and broad band F814W and F850LP calibrations, these three stars in
C.} below are at the flux level required for WFC3 grism calibration. The
brighter M, L, and T standard stars will each require a NICMOS orbit, while
faint standard requires two Nicmos orbits and one STIS orbit for complete
wavelength coverage. The STIS spectra of the M and L stars are done as ACS
calibrations in cycles 12 and 11, respectively. An additional faint WD has
already been proposed for 2 Nicmos and 4 STIS orbits in their cycle 12 programs
already. See Table 1 for a summary of the 18 orbit allocation for this program
10014. Bright stars in the V=0-6 mag range would be useful for direct
comparisons to NIST calibrated lamps. This comparison would offer the
opportunity to compare two fundamentally different realms of physics: pure
hydrogen stellar models and laboratory black body physics. Unfortunately, the
Nicmos bright limit is V=~8 for a solar analog and a 1s exposure without
defocussing the OTA. The primary Sloan standard BD+17d4708 at V=9.9 is safely
fainter than this Nicmos limit.


NICMOS Post-SAA calibration – CR Persistence Part 2

A new procedure proposed to alleviate the CR-persistence problem of NICMOS.
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
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
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

STIS 9633

STIS parallel archive proposal – Nearby Galaxies – Imaging and Spectroscopy

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
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 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

STIS/CCD 10085

STIS Pure Parallel Imaging Program: Cycle 12

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


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,
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
yield mass-loss rates but also the physical parameters {Teff, log g,
radius, mass, and metallicity}, which can then be compared to their
lower-metallicity counterparts. Parallel imaging with WFPC2 and ACS will
data useful to ourselves and others for the study of the resolved stellar
population of the Local Group galaxy most like our own.

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 pixels.

WFPC2 10082

POMS Test Proposal: WFII backup parallel archive proposal

This is a POMS test proposal designed to simulate scientific plans

WFPC2 10084

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.


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


1189-0 – Change Limits MAMA2 Threshold Voltage @ 023/0223z

                           SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq               10                       10
FGS REacq               5                          5
FHST Update             18                        18


SpaceRef staff editor.