Daily #4029

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT #4029

PERIOD COVERED: UT January 16, 2006 (DOY 016)

OBSERVATIONS SCHEDULED

ACS/HRC 10542

Charting the Sparkling Star Formation in NGC346

New, stunning V, I images of the youngest and most massive star
forming region NGC 346, in the Small Magellanic Cloud, have been
recently obtained with the HST/ACS. They reveal a myriad of small
compact clusters: some are still embedded in dust, possibly connected
by gas and dust filaments. We also discover a rich population of
pre-main sequence low mass stars {~3 -0.6 Mo} mainly distributed in
the body of NGC 346 and in these compact clusters, which formed with
the central cluster {~5My ago}, but have not reached the main sequence
yet. The immediate question that emerges is: how did star formation
occur in this region? Is there evidence for an age spread among these
clusters, that could be indicative of sequential star formation? We
are, therefore, requesting an immediate follow up investigation with
the ACS/HRC to perform a comprehensive UV/U study of the ten largest
clusters identified in the NGC 346 region, with the objective of
determining, in combination with the already available deep V, I data,
their mass function, their upper mass cut-off, whether mass
segregation is present, whether there are age variations, and what is
the impact of the stellar feedback, with the final aim to establish
how star formation has occured and progressed in this low metallicity
environment.

ACS/HRC 10607

Probing Circumstellar and Interstellar Dust with Scattered-Light
Echoes

Scattered-light echoes are one of the most powerful and efficient
probes of the structure and composition of dust in circumstellar and
interstellar {ISM} environments. Observations of light echoes provide
exact three-dimensional positions of dust while constraining its
density, grain- size and chemical make-up. Furthermore, echoes can be
used as distance indicators via polarization measurements. We propose
to take deep, high-resolution ACS/HRC images of five supernovae {SNe}.
Two of these, SNe 1991T and 1998bu, have known circumstellar echoes
that have only recently become fully resolvable with HST, and
therefore require new observations. Only four echo-producing SNe are
currently known, and in an attempt to increase this sample, we will
also observe SNe 1999bw, 2002hh, and 2004dj. All three SNe are strong
candidates for producing echoes from circumstellar and ISM dust, but
only at angular sizes that HST can resolve. With these observations,
we will use light echoes to their full advantage, to study {1} the
mass-loss histories of Type II and Ia SN progenitors, {2} the
contributions of these SNe and their progenitors to the dust content
of their galaxies, {3} the structure of gas and stars in the ISM of
external galaxies, and {4} we will independently measure the distance
to the host galaxies, including a member of the Virgo cluster, and
M96, a Type Ia cosmological distance- scale calibrator.

ACS/HRC 10627

A Snapshot Survey of Post-AGB Objects and Proto-Planetary Nebulae

We propose an ACS/HRC snapshot survey of 50 post-AGB sources, objects
which have evolved from the AGB but may or may not become planetary
nebulae {PNe}. This survey will complement existing HST images of
proto-planetary nebulae {PPNe} and PNe in addressing circumstellar
envelope morphology as a function of: 1} the progenitor star mass; 2}
the chemical composition; and 3} evolutionary stage. We will connect
the observed diversity of nebualar shapes with the main physical and
chemical conditions characterizing post-AGB objects, to identify the
mechanism that breaks the symmetry of AGB mass loss. To our knowledge,
no previous HST projects have been specifically designed to address
this issue. From our database of 360 post-AGB candidates, we have
selected approximately 50 targets, none of which have been or are
being observed with HST, to sample different central star masses,
chemical compositions, and evolutionary stages, uniformly across the
sky. These new data will also provide important constraints to a
quantitative analysis of Spitzer Space Telescope {SST} observations
planned for a similar sample of objects. We will model the HST images
and SST spectra using our axisymmetric dust code 2-Dust, to derive
dust density distributions, pole to equator density ratios, dust shell
masses, inclination angles as well as dust composition.

ACS/HRC/WFC 10514

Kuiper Belt Binaries: Probes of Early Solar System Evolution

Binaries in the Kuiper Belt are a scientific windfall: in them we have
relatively fragile test particles which can be used as tracers of the
early dynamical evolution of the outer Solar System. We propose a
Snapshot program using the ACS/HRC that has a potential discovery
efficiency an order of magnitude higher than the HST observations that
have already discovered the majority of known transneptunian binaries.
By more than doubling the number of observed objects in dynamically
hot and cold subpopulations we will be able to answer, with
statistical significance, the question of whether these groups differ
in the abundance of binaries as a result of their particular dynamical
paths into the Kuiper Belt. Today's Kuiper Belt bears the imprints of
the final stages of giant-planet building and migration; binaries may
offer some of the best preserved evidence of that long-ago era.

ACS/HRC/WFC 10729

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read
noise, the development of hot pixels and test for any source of noise
in ACS CCD detectors. The files, biases and dark will be used to
create reference files for science calibration. This programme will be
for the entire lifetime of ACS. Changes from cycle 13:- The default
gain for WFC is 2 e-/DN. As before bias frames will be collected for
both gain 1 and gain 2. Dark frames are acquired using the default
gain {2}. This program cover the period Oct, 2 2005- May, 29-2006. The
second half of the program has a different proposal number: 10758.

ACS/WFC 10496

Decelerating and Dustfree: Efficient Dark Energy Studies with
Supernovae and Clusters

We propose a novel HST approach to obtain a dramatically more useful
"dust free" Type Ia supernovae {SNe Ia} dataset than available with
the previous GOODS searches. Moreover, this approach provides a
strikingly more efficient search-and-follow-up that is primarily pre-
scheduled. The resulting dark energy measurements do not share the
major systematic uncertainty at these redshifts, that of the
extinction correction with a prior. By targeting massive galaxy
clusters at z 1 we obtain a five-times higher efficiency in
detection of Type Ia supernovae in ellipticals, providing a
well-understood host galaxy environment. These same deep cluster
images then also yield fundamental calibrations required for future
weak lensing and Sunyaev-Zel'dovich measurements of dark energy, as
well as an entire program of cluster studies. The data will make
possible a factor of two improvement on supernova constraints on dark
energy time variation, and much larger improvement in systematic
uncertainty. They will provide both a cluster dataset and a SN Ia
dataset that will be a longstanding scientific resource.

ACS/WFC 10543

Microlensing in M87 and the Virgo Cluster

Resolving the nature of dark matter is an urgent problem. The results
of the MACHO survey of the Milky Way dark halo toward the LMC indicate
that a significant fraction of the halo consists of stellar mass
objects. The VATT/Columbia survey of M31 finds a similar lens fraction
in the M31 dark halo. We propose a series of observations with ACS
that will provide the most thorough search for microlensing toward
M87, the central elliptical galaxy of the Virgo cluster. This program
is optimized for lenses in the mass range from 0.01 to 1.0 solar
masses. By comparing with archival data, we can detect lenses as
massive as 100 solar masses, such as the remnants of the first stars.
These observations will have at least 15 times more sensitivity to
microlensing than any previous survey, e.g. using WFPC2. This is due
to the factor of 2 larger area, factor of more than 4 more sensitivity
in the I-band, superior pixel scale and longer baseline of
observations. Based on the halo microlensing results in the Milky Way
and M31, we might expect that galaxy collisions and stripping would
populate the overall cluster halo with a large number of stellar mass
objects. This program would determine definitively if such objects
compose the cluster dark matter at the level seen in the Milky Way. A
negative result would indicate that such objects do not populate the
intracluster medium, and may indicate that galaxy harassment is not as
vigorous as expected. We can measure the level of events due to the
M87 halo: this would be the best exploration to date of such a lens
population in an elliptical galaxy. Star-star lensing should also be
detectable. About 20 erupting classical novae will be seen, allowing
to determine the definitive nova rate for this giant elliptical
galaxy. We will determine if our recent HST detection of an M87
globular cluster nova was a fluke, or indicative of a 100x higher rate
of incidence of cataclysmic variables and nova eruptions in globulars
than previously believed. We will examine the populations of variable
stars, and will be able to cleanly separate them from microlensing.

ACS/WFC 10626

A Snapshot Survey of Brightest Cluster Galaxies and Strong Lensing to
z = 0.9

We propose an ACS/WFC snapshot survey of the cores of 150 rich galaxy
clusters at 0.3 z 0.9 from the Red Sequence Cluster Survey {RCS}.
An examination of the galaxian light in the brightest cluster
galaxies, coupled with a statistical analysis of the strong-lensing
properties of the sample, will allow us to contrain the evolution of
both the baryonic and dark mass in cluster cores, over an
unprecedented redshift range and sample size. In detail, we will use
the high- resolution ACS images to measure the metric {10 kpc/h}
luminosity and morphological disturbances around the brightest
clusters galaxies, in order to calibrate their accretion history in
comparison to recent detailed simulations of structure formation in
cluster cores. These images will also yield a well-defined sample of
arcs formed by strong lensing by these clusters; the frequency and
detailed distribution {size, multiplicity, redshifts} of these strong
lens systems sets strong constraints on the total mass content {and
its structure} in the centers of the clusters. These data will also be
invaluable in the study of the morphological evolution and properties
of cluster galaxies over a significant redshift range. These analyses
will be supported by extensive ongoing optical and near-infrared
imaging, and optical spectroscopy at Magellan, VLT and Gemini
telescopes, as well as host of smaller facilities.

WFPC2 10744

WFPC2 Cycle 14 Decontaminations and Associated Observations

This proposal is for the 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 check.

WFPC2 10748

WFPC2 CYCLE 14 Standard Darks

This dark calibration program obtains dark frames every week in order
to provide data for the ongoing calibration of the CCD dark current
rate, and to monitor and characterize the evolution of hot pixels.
Over an extended period these data will also provide a monitor of
radiation damage to the CCDs.

WFPC2 10778

WFPC2 WF4 Supplemental Darks

An anomaly has been found in images from the WF4 CCD in WFPC2. The WF4
CCD bias level appears to have become unstable, resulting in sporadic
images with either low or zero bias level. The severity and frequency
of the problem is rapidly increasing, and it is possible that WF4 will
soon become unusable if no work-around is found. The other three CCDs
{PC1, WF2, and WF3} appear to be unaffected and continue to operate
properly. These darks are to supplement those in program 10748 to
ensure sufficient dark frames for routine calibration. As the WF4
anomaly grows worse, we are beginning to see episodes where too many
darks are corrupted and are unusable.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10086 - REACQ(1,2,2) failed due to search radius limit exceeded on FGS 1
@ 016/14:47:31z

REAcq(1,2,2)scheduled at 016/14:42:49 failed due to Search Radius
Limit Exceeded on FGS 1 at 14:47:31. The Map at 14:50:02 showed errors
of V1=3.79, V2=-145.80, V3=0.73, RSS=145.85.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL FAILURE TIMES
FGS GSacq 08 08
FGS
REacq 06 05 016/14:47:31z
(HSTAR # 10086)
OBAD with Maneuver 27 27

SIGNIFICANT EVENTS: (None)