Status Report

NASA Hubble Space Telescope Daily Report # 3655

By SpaceRef Editor
July 16, 2004
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science




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 coronagraphic
monitoring is required to assess the changing position of the spots.

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

ACS/HRC 10204

Evolution of Light Echoes of SN 1993J

SN 1993J is the nearest SN in the last decade, and only one of seven
objects to produce confirmed light echoes. Our analyses of archival
HST/WFPC2 data revealed that the SN has illuminated at least two
light-echo structures in the galaxy M81. Those echoes appear to define
two sheets of dust, located roughly 260 ly and 770 ly in front of the
SN, which are the first, and most efficient, 3-D probes of the ISM in
M81. The echoes not only reveal the ISM’s structure, but also
constrain the density, composition and grain-size of its dust. Echoes
are transient events, and as they change on timescales shorter than a
year, continued monitoring will reveal new illuminated material,
tracing interstellar and circumstellar structure. We propose a modest
and highly efficient campaign by HST to image these and yet
undiscovered echoes toward SN 1993J. Such observations will build the
first direct 3-D map of the ISM within a million cubic parsecs of
M81’s spiral arm, and may glimpse the circumstellar environment
affected by the projenitor’s mass loss. Such results probe the nature
of extragalactic dust, reveal spatio-kinematic information about the
M81’s disk, tightly constrain its internal extinction, and under the
proper circumstances, provide an independent distance measurement to
the host galaxy.

ACS/HRC 10272

A Snapshot Survey of the Sites of Recent, Nearby Supernovae

During the past few years, robotic {or nearly robotic} searches for
supernovae {SNe}, most notably our Lick Observatory Supernova Search
{LOSS}, have found hundreds of SNe, many of them in quite nearby
galaxies {cz < 4000 km/s}. Most of the objects were discovered before
maximum brightness, and have follow-up photometry and spectroscopy;
they include some of the best-studied SNe to date. We propose to
conduct a snapshot imaging survey of the sites of some of these nearby
objects, to obtain late-time photometry that {through the shape of the
light and color curves} will help reveal the origin of their lingering
energy. The images will also provide high-resolution information on
the local environment of SNe that are far superior to what we can
procure from the ground. For example, we will obtain color-color and
color-magnitude diagrams of stars in these SN sites, to determine
their progenitor masses and constraints on the reddening. Recovery of
the SNe in the new HST images will also allow us to actually pinpoint
their progenitor stars in cases where pre-explosion images exist in
the HST archive. Use of ACS rather than WFPC2 will make our snapshot
survey even more valuable than our Cycle 9 survey. This Proposal is
complementary to our Cycle 13 archival proposal, in which we outline a
plan for using existing HST images to glean information about SN


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 10046

CCD Hot Pixel Annealing

Hot pixel annealing will be performed once every 4 weeks. The CCD TECs
will be turned off and heaters will be activated to bring the detector
temperatures to about +20C. This state will be held for approximately
12 hours, after which the heaters are turned off, the TECs turned on,
and the CCDs returned to normal operating condition. To assess the
effectiveness of this procedure, a bias and two dark images will be
taken after the annealing procedure for both WFC and HRC. The HRC
darks are taken in parallel with the WFC darks.

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.

NIC/NIC3 10226

The NICMOS Grism Parallel Survey

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.

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.

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 10175

STIS Snapshot Survey of Boron Abundances in Early-B Stars

Boron abundances in massive stars provide a unique constraint for new
theoretical models of stellar evolution that include rotation. We
propose to use STIS to measure the B III doublet near 2066 Angstroms
in a large sample of early-B stars. A high priority will be placed on
obtaining abundances for several stars in each of a number of
different young clusters, associations, and star forming regions. This
will allow quantitative comparison with theoretical predictions of
rotationally driven mixing in early B stars as function of mass, age,
and rotation rate. Since boron abundance measurements are not possible
for large vsin{i} values, and sin{i} is not known for individual
stars, a large sample is required to statistically test the
predictions of boron depletion as a function of the true rotation
rate. For bright nearby stars {25 targets} we will use the G230MB
grating and obtain very high S/N {>200:1}. This avoids the need for an
ND filter which would discard 99% of the photons. Spectral synthesis
techniques will allow us to derive accurate abundances despite the
moderate resolution of this grating, even for stars with relatively
high vsin{i} values. This is especially important in testing
rotational models, as current abundance measurements are mostly for
stars with much lower than average rotation rates. For fainter, more
distant stars {27 targets} we will use the E230M or E230H grating with
the 0.2×0.2 aperture.


Probing the High Redshift Universe with Quasar Emission Lines

The quasar epoch is believed to be associated with the birth of the
most massive galaxies, a time marked by rapid star formation and
evolution. Quasar emission lines can reveal the chemical evolution and
physical state of gas in the very center of these galaxies. Analysis
of the observed line strengths, using tools that have recently become
available, implies that the chemical composition of the emitting gas
correlates with quasar luminosity in a way that is suggestive of the
known galactic mass/luminosity/metallicity correlations. The emission
lines can also reveal the form of the ionizing radiation field emitted
by the central object. Understanding the evolution of the central
powerhouse is important for black hole accretion physics and because
its spectrum is likely to dominate the ionization of the IGM. There
are many high-ionization permitted emission lines in the region below
1000A rest wavelength that can provide important new constraints on
these measurements. Thus, there is a critical need for spectra over
the full rest-wavelength range ~ 600A through the UV. Through a pilot
Cycle 10 archival study, we have identified the QSO HE 1122-1648 as an
optimal object for such a study. This QSO has a sufficiently high
redshift {z = 2.4} so that we can see down to very short rest
wavelengths {463A} in observed-wavelength regions where STIS has high
sensitivity, and lies on a line of sight with an unusually low density
of intervening Ly-alpha absorber clouds. A high-quality spectrum of
this object will have implications for the ionization of the IGM and
will leverage the unique UV capabilities of HST to complement the
galaxy formation studies that NGST will do at higher redshift.

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           07                           07
FGS REacq           05                            05
FHST Update        12                            12


SpaceRef staff editor.