Status Report

NASA Hubble Space Telescope Daily Report # 3660

By SpaceRef Editor
July 23, 2004
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science




ACS/HRC 10255

A Never Before Explored Phase Space: Resolving Close White Dwarf / Red
Dwarf Binaries

We propose an ACS Snapshot imaging survey to resolve a well-defined
sample of highly probable white dwarf plus red dwarf close binaries.
These candidates were selected from a search for white dwarfs with
infrared excess from the 2MASS database. They represent unresolved
systems {separations less than approximately 2″ in the 2MASS images}
and are distributed over the whole sky. Our HST+ACS observations will
be sensitive to a separation range {1-20 AU} never before probed by
any means. The proposed study will be the first empirical test of
binary star parameters in the post-AGB phase, and cannot be
accomplished from the ground. By resolving as few as 20 of our ~100
targets with HST, we will be able to characterize the distribution of
orbital semi-major axes and secondary star masses.


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.


Tracing the History of Cosmic Expansion to z~2 with Type Ia Supernovae

Type Ia supernovae {SNe Ia} provide the only direct evidence for an
accelerating universe, an extraordinary result that needs the most
rigorous test. The case for cosmic acceleration rests on the
observation that SNe Ia at z = 0.5 are about 0.25 mag fainter than
they would be in a universe without acceleration. A powerful and
straightforward way to assess the reliability of the SN Ia measurement
and the conceptual framework of its interpretation is to look for
cosmic deceleration at z > 1. This would be a clear signature of a
mixed dark-matter and dark-energy universe. Systematic errors in the
SNe Ia result attributed to grey dust or cosmic evolution of the SN Ia
peak luminosity would not show this change of sign. We have obtained a
toehold on this putative “epoch of deceleration” with SN 1997ff at z
= 1.7, and 3 more at z > 1 from our Cycle 11 program, all found and
followed by HST. However, this is too important a test to rest on just
a few objects, anyone of which could be subject to a lensed
line-of-sight or misidentification. Here we propose to extend our
measurement with observations of twelve SNe Ia in the range 1.0 < z < 1.5 or 6 such SNe Ia and 1 ultradistant SN Ia at z = 2, that will be discovered as a byproduct from proposed Treasury and DD programs. These objects will provide a much firmer foundation for a conclusion that touches on important questions of fundamental physics.


Galaxy Evolution During Half the Age of the Universe: ACS imaging of
rich galaxy clusters

Detailed studies of nearby galaxies {z<0.05} have shown that galaxies have very complex histories of formation and evolution involving mergers, bursts of star formation, and morphological changes. Even so, the global properties of the galaxies {radii, luminosities, rotation velocities, velocity dispersions, and absorption line strengths} follow a number of very tight {empirical} scaling relations, e.g. the Tully-Fisher relation and the Fundamental Plane. These relations place constraints on models for galaxy evolution. The results for nearby galaxies rely on high signal-to-noise spectroscopy and multi-color photometry. With the Gemini Telescopes and the Hubble Space Telescope {HST} it is possible to carry out similar detailed studies of galaxies at much larger redshifts, up to z~1.0, equivalent to half the age of the Universe. We have started a project using the scaling relations and aimed at studying the galaxy evolution over the last half of the age of the Universe. The project is based on a large database of spectroscopy and photometry of galaxies in 15 X-ray selected clusters of galaxies with redshifts between 0.15 and 1.0. Spectroscopic observations are being obtained using both Gemini Telescopes; we have observed 6 clusters so far, covering from z=0.18 to z=0.83. We propose to use HST/ACS to image the clusters and determine the morphologies and measure the sizes of the galaxies. At this time we ask for 26 orbits to image four of the clusters in our sample.

ACS/WFC 10057

ACS Ramp Filter Calibration

We request 3 orbits to observe a well-calibrated region in the Orion
Nebula with the primary goal of deriving monochromatic L-flats at
specific central wavelengths {lambda_c} for {a} WFC {inner+outer}
Halpha {FR716N, FR782N} and [OIII] {FR551N, FR601N} ramp filters. {b}
WFC middle ramp filters {FR388N, FR459M, FR505N, FR6546N, FR914M}.{c}
HRC middle ramp filters {FR388N, FR459M, FR505N, FR656N, FR914M}. As a
secondary goal, we will get an independent check of the wavelength
calibration which will be provided by the IDT team from the Cycle 11
program 9671. We request 1.5 CVZ orbits to observe two well-calibrated
standard star fields in 47 Tuc with the primary goal of deriving WFC
and HRC continuum L-flats for three middle {WFC1-MRAMP} filters:
FR656N, FR388N, and FR505N. These filters are selected as they are
frequently used to map the Halpha 6563 A, [OII] 3727A, and [OIII]
5007A lines and they include the least {FR388N} and most {FR505N}
uniform ramps, based on ground data {ISR ACS 02-01}. These 3 filters
should provide a good baseline for testing our approach and gauging
the range of non-uniformity in the continuum L-flats. For good spatial
sampling, the 2 fields are selected with stellar densities appropriate
to WFC and HRC. For good spectral sampling we will step in the central
wavelength in steps of 80 A, with 30s exposure at each lambda_c
providing good S/N for V=15-20 mag stars. We will use 2K subarrays to
reduce the frequency of buffer dumps.

ACS/WFC 10158

ACS Observations of the Gravitational Lens B1608+656: Characterizing
the Einstein Ring

We request time to obtain ACS deep images of the B1608+656
gravitational lens system to fully characterize its enclosing Einstein
ring with high signal-to-noise ratio {SNR}. These data will allow us
to determine the gravitational potential of the lens, locally, to
several percent accuracy and, combined with the three independent time
delays, measure H_0 to much better than 10% precision. For this goal,
we have developed powerful new lens modeling codes that make use of
the full brightness distribution of the Einstein ring in lens systems.
The B1608+656 system is ideal for our new code. It has precisely
measured time delays, a well-determined stellar velocity dispersion,
and an Einstein ring that is not dominated by the lensed nuclear
emission of the background source. When combined with high-SNR images
of Einstein rings, the new modeling codes provide qualitatively
different and much improved analysis of the ring emission than was
previously possible. The proposed ACS observations will reach the SNR
at which the new modeling code can be fully exploited {SNR=5 per
pixel}. Our simulations show that these new data will allow us to
reduce the total uncertainties in H_0 derived from the system by at
least a factor of two, to the 5-7% level for this system.


SAINTS – Supernova 1987A Intensive Survey

SAINTS is a program to observe SN 1987A, the brightest supernova in
383 years, as it transforms into supernova remnant {SNR} 1987A, the
youngest supernova remnant. HST is the unique and perfect match in
scale and in field for spatially-resolved observations of SN 1987A.
Rapid changes are taking place in a violent encounter between the
fastest-moving debris and the circumstellar ring. This one-time-only
event, leading to suddenly appearing hotspots and new emission that
can reveal previously hidden gas, is powered by shocks that can be
studied simultaneously with HST and with Chandra to great advantage.
Both the optical and X-ray flux from the ring are rising rapidly so
prompt observations are needed in Cycle 13. Our previous observations
reveal a remarkable reverse shock moving upstream through the
expanding debris. The reverse shock provides a powerful tool for
dissecting the radial structure of the vanished star. The debris from
the explosion itself, still excited by radioactivity, is now well
resolved by ACS and seen to be aspherical, providing direct clues to
the mechanism of the explosion. Many questions about SN 1987A remain
unanswered. SAINTS is a comprehensive attempt to use HST to establish
the facts of SN 1987A, help to answer interesting questions, and to
observe the birth of SNR 1987A.

NIC1 9833

T Dwarf Companions: Searching for the Coldest Brown Dwarfs

Faint companions to known stars have historically led to the discovery
of new classes of stellar and substellar objects. Because these
discoveries are typically limited by the flux ratio of the components
in the system, the intrinsically faintest companions are most
effectively identified around the intrinsically faintest primaries. We
propose to use NICMOS to image a sample of 22 of the coolest known
{T-type} brown dwarfs in the Solar Neighborhood in order to search for
fainter and cooler brown dwarf companions. The high spatial resolution
of the NIC 1 detector enables us to distinguish binary systems with
apparent separations greater than 0″08, or physical separations
greater than 1.2 AU at the nominal distances of the objects in our
sample. Furthermore, the substantial sensitivity of NICMOS imaging
allows us to probe companion masses of 5-50 Jupiter masses and
companion effective temperatures of 250-1300 K in a maximally
efficient manner. Based on work to date, we expect that roughly 20% of
the objects in our sample will be binary, and that one or two of these
will likely harbor a significantly fainter secondary. Hence, we expect
to find a companion cooler than any currently known brown dwarf, a
potential prototype for the next spectral class. In addition, our
investigation will add substantially to the sample of known binary
brown dwarfs, allowing improved statistical analyses of the binary
fraction, separation distribution, and mass ratio distribution of
these systems, key quantities for probing brown dwarf formation. We
will also identify optimal substellar systems for astrometric mass
measurements, a critical check for theoretical models of brown dwarfs
and extrasolar planets.

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration – CR Persistence Part 4

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.

NIC2 9875

The Fundamental Plane of Massive Gas-Rich Mergers

We propose deep NICMOS H-band imaging of a carefully selected sample
of 33 luminous, late-stage galactic mergers. This program is part of a
comprehensive investigation of the most luminous mergers in the nearby
universe, the ultraluminous infrared galaxies {ULIGs}. The
high-resolution HST images will complement an extensive set of
ground-based data that include long-slit NIR spectra from a recently
approved Large VLT Programme. This unique dataset will allow us to
derive with unprecedented precision structural -and- kinematic
parameters for a large unbiased sample of objects spanning the entire
ULIG luminosity function. These data will refine the fundamental plane
of massive gas-rich mergers and enable us to answer the following
questions: {1} Do ultraluminous mergers form elliptical galaxies, and
in particular, giant ellipticals? {2} Do ULIGs evolve into optically
bright QSOs? The results from this detailed study of massive mergers
in the local universe will be relevant to understanding galaxy
formation and evolution at earlier epochs, and in particular, the
dusty sub-mm population that accounts for more than half of the star
formation at z > 1.

NIC3 9846

The Origins of Sub-stellar Masses: Searching for the End of the IMF

Is there a preferred scale that defines the end of the IMF? We propose
to test this hypothesis by conducting a deep spectroscopic survey of
extremely low mass objects in the embedded young cluster associated
with NGC1333. At a distance of only 300pc, this cluster is one of the
nearest examples of a dense young cluster. We will be able to obtain
R=200 spectra and photometry for 40-60 cluster members with masses
between 5-40 Jupiter masses at an age of 1 Myr observed through
A{v}<10 mag. This will enable us to estimate temperatures and luminosities for all sources detected in the survey. We will compare their positions in an H-R diagram to PMS evolutionary tracks in order to estimate their ages and masses. For a solar metallicity cloud at a temperature of 10 K, the minimum mass for fragmentation is thought to be 10 Jupiter masses. A statistically significant sample of objects detected below this limit would challenge the role of hierarchical fragmentation in limiting substellar masses. The proximity of this cluster combined with the unique sensitivity, wavelength coverage, and multi-object spectroscopic capability of NICMOS on HST make this experiment possible.

STIS/CCD 10018

CCD Dark Monitor-Part 2

Monitor the darks for the STIS CCD.

STIS/CCD 10020

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/CCD 10251

SNAPSHOT Survey of SMC Planetary Nebulae

A survey of SMC planetary nebulae {PNe} is proposed to study the
co-evolution of the nebulae and their central stars, in an environment
that is chemically very metal poor. We will obtain STIS imaging and
medium-resolution slitless spectroscopy which will yield line fluxes
and nebular morphologies in important emission lines, plus magnitudes
of the central stars. From these data we will gather a harvest of
information: the nebular size, morphology, ionization structure,
density, and mass; and the central star temperature, luminosity, and
mass. We will explore the correlation found in the Galaxy of nebular
bipolarity with large progenitor star mass and with chemical
enrichment of the outer envelope during the prior AGB phase. These
relationships between PN and central star evolution will be pursued in
the SMC with a sample free of distance uncertainties and selection
biases, and in a metal-poor chemical environment that stands in sharp
contrast to the Galaxy and the LMC. The importance of this program is
two-fold: We will determine the late evolutionary paths of the most
common stars in a galaxy that, in its chemical content, mimics a young
galaxy; and we will produce a sample of extragalactic PN images and
spectra that will far exceed in number the galactic PNe already
observed with HST, providing an homogeneous database for testing the
evolutionary implications of metallicity variations in stellar

WFPC2 10071

WFPC2 CYCLE 12 Supplemental Darks Part 3/3

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


Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be

HSTAR 9488 – GSACQ(1,2,1) resulted in fine lock backup GSACQ(1,0,1).
The Gsacq(1,2,1) scheduled at 204/22:51:03 – 22:58:24 resulted in
finelock backup (1,0,1) due to search radius limit exceeded on FGS-2.
Prior FM Updates at 204/22:44:52, 204/22:47:37 both succeeded with no
trouble. There was no map scheduled because the next acquisition was
scheduled within the hour. Possible Observations affected: STIS 42,
43. Under investigation.



                          SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq              12                          12
FGS REacq              06                           06
FHST Update           15                          15


SpaceRef staff editor.