Status Report

NASA Hubble Space Telescope Daily Report # 3653

By SpaceRef Editor
July 14, 2004
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science




ACS/HRC 10130

Systemic Proper Motions of the Magellanic Clouds from Astrometry with
ACS: II. Second Epoch Images

We request second epoch observations with ACS of Magellanic Cloud
fields centered on the 40 quasars in the LMC and SMC for which we have
first epoch Cycle 11 data. The new data will determine the systemic
proper motion of the Clouds. An extensive astrometric analysis of the
first epoch data shows that follow-up observations with a two year
baseline will allow us to measure the proper motion of the clouds to
within 0.022 mas/year in each of the two orthogonal directions
{assuming that we can image 25 quasars, i.e., with a realistic
Snapshot Program completion rate}. The best weighted combination of
all previous measurements has a seven times larger error than what we
expect. We will determine the proper motion of the clouds with 2%
accuracy. When combined with HI data for the Magellanic Stream this
will constrain both the mass distribution in the Galactic Halo and
theoretical models for the origin of the Magellanic Stream. Previous
measurements are too crude for such constraints. Our data will provide
by far the most accurate proper motion measurement for any Milky Way


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.

ACS/WFC 10248

Current star formation in young, compact clusters in the Small
Magellanic Cloud

The Small Magellanic Cloud {SMC} offers a deep, resolved stellar
population that leverages fundamental parameters {metallicity, dust
content} with respect to the Milky Way and to its most studied
counterpart, the LMC. Its subsolar metallicity makes it the best
analog to the large majority of dwarf irregulars, and gives us the
possibility to study star formation and evolution in an environment
with the closest {available} resemblance to the early universe. Young,
compact clusters are ideal laboratories to investigate how these
fundamental differences affect star and cluster formation and
evolution. We are therefore, proposing, to use ACS and NICMOS to
perform a in depth study of the “resolved” stellar population in the
four youngest compact clusters in the SMC. The observations, spanning
the UV to the near-IR, will reach the subsolar domain, and will
address the following fundamental questions: Does the IMF follow the
universal Salpeter’s law? Is mass segregation prevalent in the SMC
clusters as in LMC clusters? Is on-going star formation present, where
and how? What is the role of massive star feedback? The four proposed
clusters span an age range from 3-20 Myr, and sample spatially
different regions of the SMC. The synergy with NICMOS will permit full
characterization of existing pre main sequence stars, if detected.
This proposal is part of a coordinated HST and ground-based study of
the stellar history and star formation processes in the SMC.

ACS/WFC 9751

Accurate Mass Determination of the Ancient White Dwarf ER 8 Through
Astrometric Microlensing

We propose to determine the mass of the very cool white dwarf ER 8
through astrometric microlensing. We have predicted that ER 8 will
pass very close to a 15th-mag background star in January 2006, with an
impact parameter of less than 0.05 arcsec. As it passes in front, it
will cause a deflection of the background star’s image by >8
milliarcsec, an amount easily detectable with HST/FGS. The
gravitational deflection angle depends only on the distances and
relative positions of the stars, and on the mass of the white dwarf.
Since the distances and positions can be determined precisely before
the event, the astrometric measurement offers a unique and direct
method to measure the mass of the white dwarf to high accuracy {<5%}. Unlike all other stellar mass determinations, this technique works for single stars {but only if they are nearby and of sufficient mass}. The mass of ER 8 is of special interest because it is a member of the Galactic halo, and appears to be the oldest known field white dwarf. This object can thus set a lower limit on the age of the Galactic halo, but since white-dwarf cooling rates depend on their masses, the mass is a necessary ingredient in the age determination. As a byproduct, we will obtain an accurate parallax for ER 8, and thus its luminosity and {from its effective temperature} its radius. Such quantities are at present rather poorly known for the coolest white dwarfs, and will provide strong constraints on white-dwarf physics.

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 10149

The Coevolution of Supermassive Black Holes and Galaxies at z~3

The existence of strong correlations between the mass of supermassive
black holes and galaxy bulge properties implies that there is an
intimate connection between their formation and evolution. How do
supermassive black holes grow and how did the correlations come about?
Is the growth of supermassive black holes coeval with the growth of
the bulge, and is a bulge necessary for AGN activity at high z? We
propose to use HST NICMOS to image 9 low-luminosity broad-line AGNs at
z~3 in the restframe B-band, identified through the Lyman-break
technique. This sample is unique because the AGN luminosities are
comparable to Seyfert-like nuclei at z~3, and thus are some of the
lowest that have been selected optically. Because of the low total
luminosity of the sample, the hosts are likely to be Lyman-break
galaxies, which are believed to be the progenitor galaxies of the
local Hubble sequence. The goal is to directly detect their host
galaxies and to separate the AGN, in order to study the host galaxy
morphology and luminosity. From measurement of the bulge luminosity
and black hole mass {through available spectra}, we will study the
black hole-bulge coevolution out to z~3. We will also compare the
luminosity and morphology of these faint AGN hosts with the more
luminous and massive host galaxies found in previous HST studies of

NIC2 10176

Coronagraphic Survey for Giant Planets Around Nearby Young Stars

A systematic imaging search for extra-solar Jovian planets is now
possible thanks to recent progress in identifying “young stars near
Earth”. For most of the proposed young {<~ 30 Myrs} and nearby {<~ 60 pc} targets, we can detect a few Jupiter-mass planets as close as a few tens of AUs from the primary stars. This represents the first time that potential analogs of our solar system - that is planetary systems with giant planets having semi-major axes comparable to those of the four giant planets of the Solar System - come within the grasp of existing instrumentation. Our proposed targets have not been observed for planets with the Hubble Space Telescope previously. Considering the very successful earlier NICMOS observations of low mass brown dwarfs and planetary disks among members of the TW Hydrae Association, a fair fraction of our targets should also turn out to posses low mass brown dwarfs, giant planets, or dusty planetary disks because our targets are similar to {or even better than} the TW Hydrae stars in terms of youth and proximity to Earth. HST cycle 13 may be the last chance to find young Solar System analogs in the coming decade. Should HST time be awarded and planetary mass candidates be found, proper motion follow-up of candidate planets will be done with ground-based AOs.

STIS 9786

The Next Generation Spectral Library

We propose to continue the Cycle 10 snapshot program to produce a Next
Generation Spectral Library of 600 stars for use in modeling the
integrated light of galaxies and clusters. This program is using the
low dispersion UV and optical gratings of STIS. The library will be
roughly equally divided among four metallicities, very low {[Fe/H] lt
-1.5}, low {[Fe/H] -1.5 to -0.5}, near-solar {[Fe/H] -0.3 to 0.1}, and
super-solar {[Fe/H] gt 0.2}, well-sampling the entire HR-diagram in
each bin. Such a library will surpass all extant compilations and have
lasting archival value, well into the Next Generation Space Telescope
era. Because of the universal utility and community-broad nature of
this venture, we waive the entire proprietary period.

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


UV extinction by dust in unexplored LMC environments

The ensemble of results from studies of the UV extinction in the Milky
Way, Magellanic Clouds {MC}, M31 and M33, indicates a complex
dependence of the dust properties with environment, where starburst
activity and metallicity are relevant factors. Work in the LMC to
date, based on IUE data, has several drawbacks: a} only supergiants
could be used, b} they all have moderate extinction, c} the IUE S/N is
limited, d} the large IUE slit may include light from other sources,
such as scattered light from dust or faint companion stars, e} studies
are confined to few {extreme} environments. We propose to obtain UV
extinction curves more accurate than previous ones {from STIS spectra
of main sequence stars with higher reddening}, sampling four
environments in the LMC with different levels of star formation
activity, including the general field, hitherto unexplored. The
results will characterize the properties of dust in different
conditions, at the LMC metallicity, which is useful to interpret
integrated properties of distant galaxies, as well as GALEX upcoming
UV surveys. A complementary study is under way with FUSE in the far-UV
range. The combined results will provide insight on the properties of
small grains.

WFPC2 10067

WFPC2 Cycle 12 Decontaminations and Associated Observations

This proposal is for the monthly WFPC2 decons. Also included are
instrument monitors tied to decons: photometric stability check, focus
monitor, pre- and post-decon internals {bias, intflats, kspots, &
darks}, UV throughput check, VISFLAT sweep, and internal UV flat

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
investigated.) None



                         SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq              9                            9
FGS REacq             11                           11
FHST Update          12                           12


SpaceRef staff editor.