Daily # 4238

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4238

PERIOD COVERED: UT November 09,10,11,12, 2006 (DOY 313,314,315,316)

OBSERVATIONS SCHEDULED

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

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.

ACS/WFC 10994

Infalling Groups and the Origin of Early-Type Galaxies

The creation of the cluster early-type galaxy sequence most likely
occurs in groups, as mergers are possible in such environments. Recent
results have shown that groups of galaxies at half of the Hubble time
show a truncated red-sequence. We are surveying two small groups that
will fall into a massive cluster by z=0, to determine the morphologies
of the group members. The truncation of the red sequence should show
up in the morphology-density relation and in an increased merger
fraction.

FGS 10927

The Weight-Watcher Program for Subdwarfs

We propose to use HST/FGS1r to measure five subdwarf spectroscopic
binaries to determine masses for the components. Their metallicities,
[Fe/H], range from -0.5 to -2.5, and their projected minimum
separations range from 9 to 24 mas. These binaries are resolvable with
HST/FGS1r but not any ground-based technique. Currently, there are
only two subdwarf systems having any mass measurements. The proposed
work will boost the total number of subdwarf systems with masses from
two to seven, and allow us to construct the first mass-luminosity
relation for low- metallicity stars.

WFPC2 10915

ACS Nearby Galaxy Survey

Existing HST observations of nearby galaxies comprise a sparse and
highly non-uniform archive, making comprehensive comparative studies
among galaxies essentially impossible. We propose to secure HST's
lasting impact on the study of nearby galaxies by undertaking a
systematic, complete, and carefully crafted imaging survey of ALL
galaxies in the Local Universe outside the Local Group. The resulting
images will allow unprecedented measurements of: {1} the star
formation history {SFH} of a 100 Mpc^3 volume of the Universe with a
time resolution of Delta[log{t}]=0.25; {2} correlations between
spatially resolved SFHs and environment; {3} the structure and
properties of thick disks and stellar halos; and {4} the color
distributions, sizes, and specific frequencies of globular and disk
clusters as a function of galaxy mass and environment. To reach these
goals, we will use a combination of wide-field tiling and pointed deep
imaging to obtain uniform data on all 72 galaxies within a
volume-limited sample extending to ~3.5 Mpc, with an extension to the
M81 group. For each galaxy, the wide-field imaging will cover out to
~1.5 times the optical radius and will reach photometric depths of at
least 2 magnitudes below the tip of the red giant branch throughout
the limits of the survey volume. One additional deep pointing per
galaxy will reach SNR~10 for red clump stars, sufficient to recover
the ancient SFH from the color-magnitude diagram. This proposal will
produce photometric information for ~100 million stars {comparable to
the number in the SDSS survey} and uniform multi-color images of half
a square degree of sky. The resulting archive will establish the
fundamental optical database for nearby galaxies, in preparation for
the shift of high-resolution imaging to the near-infrared.

ACS/WFC 10905

The Dynamic State of the Dwarf Galaxy Rich Canes Venatici I Region

With accurate distances, the nearest groups of galaxies can be
resolved in 3 dimensions and the radial component of the motions of
galaxies due to local density perturbations can be distinquished from
cosmological expansion components. Currently, with the ACS, galaxy
distances within 8 Mpc can be measured effectively and efficiently by
detecting the tip of the red giant branch {TRGB}. Of four principal
groups at high galactic latitude in this domain, the Canes Venatici I
Group {a} is the least studied, {b} is the most populated, though
overwhelmingly by dwarf galaxies, and {c} is likely the least
dynamically evolved. It is speculated that galaxies in low mass groups
may fail to retain baryons as effectively as those in high mass
groups, resulting in significantly higher mass-to-light ratios. The
CVn I Group is suspected to lie in the mass regime where the
speculated astrophysical processes that affect baryon retention are
becoming important.

ACS/WFC 10895

Closure on the IRAS "Big Four": A High Contrast Study of Epsilon
Eridani's Dust Belt in Scattered Light.

The ACS / HRC coronagraph has now demonstrated an unmatched capability
to detect dusty debris disks around bright, nearby stars. Among the
"Big Four" debris disks discovered with IRAS twenty years ago, only
Epsilon Eridani {SpT=K2V, d=3.2 pc} has yet to be targeted with ACS.
Beta Pictoris, Fomalhaut and Vega have been imaged with the ACS
coronagraph, with the recent detection of reflected light from
Fomalhaut's dust belt {Kalas, Graham & Clampin 2005}. The direct
detection of dust scattered light around Fomalhaut shows disk
structure and asymmetry that can be directly linked to dynamical
models of planetary perturbation. Here we propose to use the ACS HRC
and WFC to detect Eps Eri's dust belt. A new motivation to attempt
this observations arises from recent 350 micron images that reveal two
dust arcs ~60 AU to the southeast and northwest of the star. Contrary
to previous 850 and 450 micron maps, the northwest arc is brighter
than the southeast arc, and the northwest region has not been targeted
by previous STIS imaging at lower contrast. The optical detection of
dust features around Eps Eri would be significant because a high
resolution optical image, together with Spitzer and sub-mm images,
would help anchor dynamical models of Eps Eri's planetary system, in
addition to providing direct visual indications of disk-planet
interactions.

NIC2 10893

Sweeping Away the Dust: Reliable Dark Energy with an Infrared Hubble
Diagram

We propose building a high-z Hubble Diagram using type Ia supernovae
observed in the infrared rest-frame J-band. The infrared has a number
of exceptional properties. The effect of dust extinction is minimal,
reducing a major systematic tha may be biasing dark energy
measurements. Also, recent work indicates that type Ia supernovae are
true standard candles in the infrared meaning that our Hubble diagram
will be resistant to possible evolution in the Phillips relation over
cosmic time. High signal-to-noise measurements of 9 type Ia events at
z~0.4 will be compared with an independent optical Hubble diagram from
the ESSENCE project to test for a shift in the derived dark energy
equation of state due to a systematic bias. Because of the bright sky
background, H-band photometry of z~0.4 supernovae is not feasible from
the ground. Only the superb image quality and dark infrared sky seen
by HST makes this test possible. This experiment may also lead to a
better, more reliable way of mapping the expansion history of the
universe with the Joint Dark Energy Mission.

ACS/WFC 10882

Emission Line Snapshots of 3CR Radio Galaxies

Radio galaxies are an important class of extragalactic objects: they
are one of the most energetic astrophysical phenomena and they provide
an exceptional probe of the evolving Universe, lying typically in high
density regions but well-represented across a wide redshift range. In
earlier Cycles we carried out extensive HST observations of the 3CR
sources in order to acquire a complete and quantitative inventory of
the structure, contents and evolution of these important objects. We
discovered new optical jets, dust lanes, and revealed point-like
nuclei whose properties support AGN unified schemes. Here, we propose
to obtain ACS emission line images at low and high excitation of 3CR
sources with z0.3, both low- and classical high- power radio
galaxies, as a major enhancement to an already superb dataset. We aim
to probe fundamental relationships between warm optical line-emitting
gas, radio source structure {jets and lobes} and X-ray coronal halos.
We will combine our existing UV images with new emission- line images
to establish quantitative star formation characteristics and their
relation to dust and merging, and with emission-line excitation maps,
test theories on ionization beam patterns and luminosities from active
nuclei. We will seek jet induced star formation and knowing optical
emission-line physics, investigate quantitative jet physics. The
nuclear emission line properties of the galaxies will themselves be
established and used as ingredients in continuing tests of unified AGN
theories. The resulting database will be an incredibly valuable
resource to the astronomical community for years to come.

ACS/WFC 10880

The host galaxies of QSO2s: AGN feeding and evolution at high
luminosities

Now that the presence of supermassive black holes in the nuclei of
galaxies is a well established fact, other questions related to the
AGN phenomena still have to be answered. Problems of particular
interest are how the AGN gets fed, how the black hole evolves and how
the evolution of the black hole is related to the evolution of the
galaxy bulge. Here we propose to address some of these issues using
ACS/WFC + F775W snapshot images of 73 QSO2s with redshifts in the
range 0.3z0.4. These observations will be combined with similar
archival data of QSO1s and ground based data of Seyfert and normal
galaxies. First, we will intestigate whether interactions are the most
important feeding mechanism in high luminosity AGNs. This will be done
in a quantitative way, comparing the asymmetry indices of QSO2 hosts
with those of lower luminosity AGNs and normal galaxies. Second, we
will do a detailed study of the morphology of the host galaxies of
both QSO types, to determine if they are similar, or if there is an
evolutionary trend from QSO2s to QSO1s. The results from this project
will represent an important step in the understanding of AGN
evolution, and may also introduce a substantial modification to the
Unified Model.

ACS/WFC 10876

SL2S: The Strong Lensing Legacy Survey

Strong Gravitational Lensing is an invaluable tool to constrain the
absolute mass distribution of structures irrespective of their light
distribution. Strong Lensing has successfully been applied to single
galaxies lensing quasars into multiple images, and to massive clusters
lensing background sources into giant arcs. More recently, the Sloan
Lens ACS Survey also found numerous examples of isolated, yet massive
ellipticals lensing background galaxies into Einstein rings. We have
started the Strong Lensing Legacy Survey {SL2S} looking for strong
lenses in the 170 sq. degree CFHT-Legacy Survey, using dedicated
automated search procedures, optimized for detection of arcs and
Einstein rings. Thanks to the unsurpassed combined depth, area and
image quality of the CFHT-LS, we uncovered a new population of lenses:
the intermediate mass halo and sub-halo lenses. This new population
effectively bridges the gap between single galaxies and massive
clusters. Here, we propose to obtain SNAPSHOT ACS images of the 50
first strong lens candidates with Einstein radii 2"Re9" {found in
the first 45 sq. degrees of CFHT-LS data released}. The ACS images
will allow us to model in details the mass distribution of this new
population of lensing groups under various lensing configurations.
Using ACS images, we ultimately hope to provide a better understanding
of the formation of structures by studying the lensing signatures of
the key population of galaxy groups.

ACS/WFC 10875

A Snapshot Survey of The Most Massive Clusters of Galaxies

We propose the continuation of our highly successful Cycle14 snapshot
survey of a sample of 123 very X-ray luminous clusters in the redshift
range 0.3-0.7. As demonstrated by the 21 snapshots obtained so far in
Cycle14 these systems frequently exhibit strong gravitational lensing
as well as spectacular examples of violent galaxy evolution. The
proposed observations will provide important constraints on the
cluster mass distributions, the physical nature of galaxy-galaxy and
galaxy-gas interactions in cluster cores, and a set of optically
bright, lensed galaxies for further 8-10m spectroscopy. Acknowledging
the broad community interest in this sample we waive our data rights
for these observations.

ACS/HRC 10860

The largest Kuiper belt object

The past year has seen an explosion in the discoveries of Pluto-sized
objects in the Kuiper belt. With the discoveries of the
methane-covered 2003 UB313 and 2005 FY9, the multiple satellite system
of 2003 EL61, and the Pluto-Charon analog system of Orcus and its
satellite, it is finally apparent that Pluto is not a unique oddball
at the edge of the solar system, but rather one of a family of
similarly large objects in the Kuiper belt and beyond. HST
observations over the past decade have been critical for understanding
the interior, surface, and atmosphere of Pluto and Charon. We propose
here a comprehensive series of observations designed to similarly
expand our knowledge of these recently discovered Pluto-sized and
near-Pluto-sized Kuiper belt objects. These observations will measure
objects' sizes and densities, explore the outcome of collisions in the
outer solar system, and allow the first ever look at the interior
structure of a Kuiper belt object. Our wide field survey that
discovered all of these objects is nearly finished, so after five
years of continuous searching we are finally almost complete in our
tally of these near-Pluto-sized objects. This large HST request is the
culmination of this half-decade search for new planetary-sized
objects. As has been demonstrated repeatedly by the approximately 100
previous orbits devoted to the study of Pluto, only HST has the
resolution and sensitivity for detailed study of these distant
objects.

ACS/HRC 10833

Host Galaxies of Reverberation Mapped AGNs

We propose to obtain unsaturated high-resolution images of 17
reverberation-mapped active galactic nuclei in order to remove the
point-like nuclear light from each image, thus yielding a
"nucleus-free" image of the host galaxy. This will allow investigation
of host galaxy properties: our particular interest is determination of
the host-galaxy starlight contribution to the reverberation-mapping
observations. This is necessary {1} for accurate determination of the
relationship between the AGN nuclear continuum flux and the size of
the broad Balmer-line emitting regions of AGNs, which is important in
estimating black hole masses for large samples of QSOs, and {2} for
accurate determination of the bolometric luminosity of the AGN proper.
Through observations in Cycles 12 and 14, we have obtained or will
obtain images of 18 of the 35 objects in the reverberation-mapping
compilation of Peterson et al. {2004}. These observations revealed
that the host-galaxy contribution, even in the higher-luminosity AGNs,
is higher than expected and that all of the reverberation-mapped AGNs
will have to be observed, not just the lower-luminosity sources; each
source is different, and each source is important. Therefore we
request time to observe the 17 remaining reverberation-mapped AGNs.

ACS/WFC 10831

A new wide-separation Einstein Cross at z=2.7

We propose ACS F555W and F814W imaging observations of a new
wide-separation Einstein Cross selected from SDSS spectroscopy through
a bright anomalous emission line and confirmed recently with Keck
imaging and spectroscopy. The source galaxy is a moderately luminous
{L~0.2L*} Lyman-alpha emitter at z=2.699, which is magnified and
extended by more than a factor of twenty, making it one of the most
accessible high-redshift bright Ly-a emitters on the sky. Its apparent
flux is only 1.2 magnitudes fainter than MS1612-cB58, making this an
ideal system for detailed study of the metallicity and initial mass
function of a high-redshift star forming galaxy. The Einstein Radius
is ~1.8arcsec, one of the widest known, making future spectroscopic
ground-based followup optimal. This angle subtends ~5 kpc at the lens
galaxy at z=0.331. The high resolution, high signal to noise imaging
we propose to obtain will allow us to build accurate lensing models,
including source reconstructions; combined with existing and planned
Keck spectroscopy, will make possible a map of the host dark matter
halo density profile to greater than one effective light radius; and
will reveal lower surface brightness features associated with the
bright star-forming knot lensed into the Cross. Finally, it will be an
exquisite Hubble Heritage galaxy, which will be indispensable for many
other applications. We are requesting a very modest proprietary
period, in order to provide high-level reductions and ancillary data
publically available simultaneously.

ACS/WFC 10829

Secular Evolution at the End of the Hubble Sequence

The bulgeless disk galaxies at the end of the Hubble Sequence evolve
at a glacial pace relative to their more violent, earlier-type
cousins. The causes of their internal, or secular evolution are
important because secular evolution represents the future fate of all
galaxies in our accelerating Universe and is a key ingredient to
understanding galaxy evolution in lower-density environments at
present. The rate of secular evolution is largely determined by the
stability of the cold ISM against collapse, star formation, and the
buildup of a central bulge. Key diagnostics of the ISM's stability are
the presence of compact molecular clouds and narrow dust lanes.
Surprisingly, edge-on, pure disk galaxies with circular velocities
below 120 km/s do not appear to contain such dust lanes. We propose to
obtain ACS/WFC F606W images of a well-selected sample of extremely
late-type disk galaxies to measure the characteristic scale size of
the cold ISM and determine if they possess the unstable, cold ISM
necessary to drive secular evolution. Our sample has been carefully
constructed to include disk galaxies above and below the critical
circular velocity of 120 km/s where the dust properties of edge-on
disks change so remarkably. We will then use surface brightness
profiles to search for nuclear star clusters and pseudobulges, which
are early indicators that secular evolution is at work, as well as
measure the pitch angle of the dust lanes as a function of radius to
estimate the central mass concentrations.

NIC2, ACS/WFC 10802

SHOES-Supernovae, HO, for the Equation of State of Dark energy

The present uncertainty in the value of the Hubble constant {resulting
in an uncertainty in Omega_M} and the paucity of Type Ia supernovae at
redshifts exceeding 1 are now the leading obstacles to determining the
nature of dark energy. We propose a single, integrated set of
observations for Cycle 15 that will provide a 40% improvement in
constraints on dark energy. This program will observe known Cepheids
in six reliable hosts of Type Ia supernovae with NICMOS, reducing the
uncertainty in H_0 by a factor of two because of the smaller
dispersion along the instability strip, the diminished extinction, and
the weaker metallicity dependence in the infrared. In parallel with
ACS, at the same time the NICMOS observations are underway, we will
discover and follow a sample of Type Ia supernovae at z 1. Together,
these measurements, along with prior constraints from WMAP, will
provide a great improvement in HST's ability to distinguish between a
static, cosmological constant and dynamical dark energy. The Hubble
Space Telescope is the only instrument in the world that can make
these IR measurements of Cepheids beyond the Local Group, and it is
the only telescope in the world that can be used to find and follow
supernovae at z 1. Our program exploits both of these unique
capabilities of HST to learn more about one of the greatest mysteries
in science.

ACS/HRC/WFC 10758

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 May, 31 2006- Oct, 1-2006. The
first half of the program has a different proposal number: 10729.

NIC1/NC2/NC3 10723

Cycle 14 NICMOS dark current, shading profile, and read noise
monitoring program

The purpose of this proposal is to monitor the dark current, read
noise, and shading profile for all three NICMOS detectors throughout
the duration of Cycle 14. This proposal is a slightly modified version
of proposal 10380 of cycle 13 and 9993 of cycle12 that we cut down
some exposure time to make the observation fit within 24 orbits.

FGS 10611

Precise Distances to Nearby Planetary Nebulae

We propose to carry out astrometry with the FGS to obtain accurate and
precise distances to four nearby planetary nebulae. In 1992, Cahn et
al. noted that ``The distances to Galactic planetary nebulae remain a
serious, if not THE most serious, problem in the field, despite
decades of study.'' Twelve years later, the same statement still
applies. Because the distances to planetary nebulae are so uncertain,
our understanding of their masses, luminosities, scale height, birth
rate, and evolutionary state is severely limited. To help remedy this
problem, HST astrometry can guarantee parallaxes with half the error
of any other available approach. These data, when combined with
parallax measurements from the USNO, will improve distance
measurements by more than a factor of two, producing more accurate
distances with uncertainties that are of the order of ~6%. Lastly,
most planetary nebula distance scales in the literature are
statistical. They require several anchor points of known distance in
order to calibrate their zero point. Our program will provide "gold
standard" anchor points by the end of 2006, a decade before any
anticipated results from future space astrometry missions.

ACS/WFC 10605

Quantifying Star Formation and Feedback: The M81 Group Dwarf Galaxies

Studies of the impact of star formation via stellar winds and
supernovae {'feedback'} on the properties of a galaxy are of
fundamental importance to understanding galaxy evolution. One crucial
aspect in these studies is a precise census of the recent star
formation in a galaxy. The aim of this proposal is to obtain spatially
resolved star formation histories with a time resolution of roughly 30
Myr over the last 500 Myr in a carefully designed sample using the
absolutely unique capabilities of the ACS. Our sample comprises 10
galaxies in the M81 group which is host to a wide diversity of dwarf
star forming galaxies. They span ranges of 6 magnitudes in luminosity,
1000 in current star formation rate, and 0.5 dex in metallicity. The
ACS observations will allow us to directly observe the strength and
spatial relationships of all of the star formation in these galaxies
in the last 500 Myr. We can then quantify the star formation and
measure {1} the fraction of star formation that is triggered by
feedback, {2} the fraction of star formation that occurs in clusters
and associations, and {3} to what degree future star formation is
governed by the feedback from previous star formation. The ACS
observations will be complemented with high-quality ancillary data
collected by our team for all galaxies {e.g., Spitzer, UV/optical/NIR,
VLA HI}. We will calculate the energy created by star formation events
and compare it to the estimated energy deposited into the local ISM.
This will enable us to construct prescriptions of how star formation
and feedback depend on metallicity, size, gas content, and current
star formation rates in galaxies. Our resolved star formation maps
will be compared with star formation rates inferred from H-alpha, UV,
and IR observations - allowing an independent calibration of these
techniques. Recent ACS imaging by us of one galaxy in the same group
clearly demonstrates the feasibility of the proposed program. Most of
the sample galaxies are located in the CVZ, making this an extremely
efficient program.

ACS/WFC 10587

Measuring the Mass Dependence of Early-Type Galaxy Structure

We propose two-color ACS-WFC Snapshot observations of a sample of 118
candidate early- type gravitational lens galaxies. Our lens-candidate
sample is selected to yield {in combination with earlier results} an
approximately uniform final distribution of 40 early-type strong
lenses across a wide range of masses, with velocity dispersions {a
dynamical proxy for mass} ranging from 125 to 300 km/s. The proposed
program will deliver the first significant sample of low-mass
gravitational lenses. All of our candidates have known lens and source
redshifts from Sloan Digital Sky Survey data, and all are bright
enough to permit detailed photometric and stellar- dynamical
observation. We will constrain the luminous and dark-matter mass
profiles of confirmed lenses using lensed-image geometry and
lens-galaxy structural/photometric measurements from HST imaging in
combination with dynamical measurements from spatially resolved
ground-based follow-up spectroscopy. Hence we will determine, in
unprecedented detail, the dependence of early-type galaxy mass
structure and mass-to-light ratio upon galaxy mass. These results will
allow us to directly test theoretical predictions for halo
concentration and star-formation efficiency as a function of mass and
for the existence of a cuspy inner dark- matter component, and will
illuminate the structural explanation behind the fundamental plane of
early-type galaxies. The lens-candidate selection and confirmation
strategy that we propose has been proven successful for high-mass
galaxies by our Cycle 13 Snapshot program {10174}. The program that we
propose here will produce a complementary and unprecedented lens
sample spanning a wide range of lens-galaxy masses.

ACS/HRC 10556

Neutral Gas at Redshift z=0.5

Damped Lyman-alpha systems {DLAs} are used to track the bulk of the
neutral hydrogen gas in the Universe. Prior to HST UV spectroscopy,
they could only be studied from the ground at redshifts z1.65.
However, HST has now permitted us to discover 41 DLAs at z1.65 in our
previous surveys. Followup studies of these systems are providing a
wealth of information about the evolution of the neutral gas phase
component of the Universe. But one problem is that these 41
low-redshift systems are spread over a wide range of redshifts
spanning nearly 70% of the age of the Universe. Consequently, past
surveys for low-redshift DLAs have not been able to offer very good
precision in any small redshift regime. Here we propose an ACS-HRC-
PR200L spectroscopic survey in the redshift interval z=[0.37, 0.7]
which we estimate will permit us to discover another 41 DLAs. This
will not only allow us to double the number of low-redshift DLAs, but
it will also provide a relatively high-precision regime in the
low-redshift Universe that can be used to anchor evolutionary studies.
Fortunately DLAs have high absorption equivalent width, so
ACS-HRC-PR200L has high-enough resoultion to perform this proposed
MgII-selected DLA survey.

ACS/WFC 10500

Exploring the Bottom End of the White Dwarf Cooling Sequence in the
Galactic Open Cluster NGC2158

The recent discovery by our group of an unexpectedly bright and still
unexplained peak in the white dwarf {WD} luminosity function {LF} of
the metal rich, old open cluster NGC6791 casts serious doubts on our
understanding of the physical process which rules the formation and
the cooling of WDs. In order to investigate whether the same problem
is present in other open clusters with different ages and
metallicities, we propose deep ACS/HST observations reaching the
bottom end of the WD LFs, for the first time in a young and so
popolous Galactic open cluster: NGC2158.

ACS/HRC 10498

Detecting the progenitors of core-collapse supernovae

Modern supernovae searches in the nearby Universe are discovering
large numbers of SNe which have massive star progenitors {Types II, Ib
and Ic}. The extensive HST image archives within ~20Mpc enables their
indvidual bright stellar content to be resolved. As massive, evolved
stars are the most luminous single objects in a galaxy, the progenitos
of core-collapse SNe should be directly detectable on pre-explosion
images. Two recent highlights of our ongoing HST programme are that we
have detected the first red supergiant progenitor of a normal type II
supernova and shown that SN1993J came from a binary system by
detecting the companion star at the position of the SN. We have
detected a further two progenitor stars of normal type II-P
supernovae, set mass limits on a further 7 and suggest that faint type
II supernovae are unlikely to come from the collapse of very massive
stars which form black holes. These discoveries are providing strong
constraints on theoretical models of pre-supernova evolution and the
origin of the supernova types. We request time to continue this
successful project and require ACS observations of future SNe which
are discovered in galaxies closer than 20Mpc which have pre-explosion
HST archive images available. This will allow the SNe to be precisely
positioned on the pre-explosion images. We have set a final goal for
this project of determining masses and types, or setting restrictive
mass-limits for 30 supernovae.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10502 - GSACQ(2,3,3) failed to RGA hold due to STOP flag for FGS 2

Initial indication was ROOL F2SSCEA flaggin low with a value of -10.24
at 15:28:06. The other mnemonics falgged at 15:28:20 (QF2STOPF)
15:28:22 (STOP) 15:28:27 (QF2SSDIF AND Q3SSDIF) 1st ODAB: V1 -2011.25,
V2 -1533.54, V3 2349.67, RSS 3452.22 2nd ODAB: V1 -4.93, V2 3.69, V3
-0.79, RSS 6.21 MAP: V1 -0.86, V2 12.73, V3 -1.78, RSS 12.89

10503 - GSAcq(2,1,1) failed to RGA Hold Control

Upon acquisition of signal at 316/09:16:16, GSAcq(2,1,1) scheduled at
316/08:56:07 - 09:04:12 was observed to have failed to RGA Hold due to
stop flag (QF1STOPF) on FGS-1. Pre-acquisition OBADs attitude error
corrections not available. Post-acquisition OBAD/MAP had 3-axis (RSS)
value of 13.08 arcseconds.

10504 - GSacq(2.3.3) failed due to scan step limit exceeded for FGS 2

At AOS (316/22:03:30) GSAcq (2,3,3), scheduled 316/21:44:02 had failed
to RGA control due to Scan Step Limit Exceeded on FGS 2. OBAD MAP RSS
value = 13.63 a-s.

10505 - OBAD Failed Identification

At 317/01:00:50, OBAD2 using trackers FHST-1 and FHST-2 failed. One
486 ESB message 1902 (OBAD Failed Identification) was received. OBAD2
had (RSS) value of 26750.24 arcseconds.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 28 25
FGS REacq 12 12
OBAD with Maneuver 78 78

SIGNIFICANT EVENTS: (None)