NASA Hubble Space Telescope Daily Report # 3438 (part 1)

HUBBLE SPACE TELESCOPE

DAILY REPORT # 3438

PERIOD COVERED: DOYs 241-244

OBSERVATIONS SCHEDULED

ACS 9984

Cosmic Shear With ACS Pure Parallels

Small distortions in the shapes of background galaxies by foreground
mass provide a powerful method of directly measuring the amount and
distribution of dark matter. Several groups have recently detected
this weak lensing by large-scale structure, also called cosmic shear.
The high resolution and sensitivity of HST/ACS provide a unique
opportunity to measure cosmic shear accurately on small scales. Using
260 parallel orbits in Sloan textiti {F775W} we will measure for the
first time: beginlistosetlength sep0cm setlengthemsep0cm setlength
opsep0cm em the cosmic shear variance on scales <0.7 arcmin, em the
skewness of the shear distribution, and em the magnification effect.
endlist Our measurements will determine the amplitude of the mass
power spectrum sigma_8Omega_m^0.5, with signal-to-noise {s/n} ~ 20,
and the mass density Omega_m with s/n=4. They will be done at small
angular scales where non-linear effects dominate the power spectrum,
providing a test of the gravitational instability paradigm for
structure formation. Measurements on these scales are not possible
from the ground, because of the systematic effects induced by PSF
smearing from seeing. Having many independent lines of sight reduces
the uncertainty due to cosmic variance, making parallel observations
ideal.

STIS/ACS/HRC 9975

Ozone, Condensates, and Dust in the Martian Atmosphere

We propose to utilize the unique UV capabilities of STIS and ACS/HRC
in order to study the spatial and seasonal variations in ozone,
condensates, and dust in the Martian atmosphere. The data obtained
will be critical in addressing recent breakthroughs in understanding
the basic radiative, transport, and microphysical processes that
provide for both long-term and short-term balance within the global
Mars climate system. The proposal includes both Cycle 11 & 12
observations in order to span the classic dust storm season on Mars
and provide the first good opportunity for HST to observe a dusty
atmosphere on the planet. The UV observations will complement visible
and IR observations that will be made during the Mars Global Surveyor
Extended Mission and will provide support for the future UV
observations of MARCI on the 2005 Mars Reconnaissance Orbiter.

ACS/HRC/WFC 9919

The Morphological, Photometric, and Spectroscopic Properties of
Intermediate Redshift Cluster Galaxies:

New and fundamental constraints on the evolutionary state of high
redshift clusters will be made by obtaining deep, multiband images
{SDSS r, i, z} over the central 1.5 Mpc regions of seven distant
clusters in the range 0.76 < z < 1.27. The ACS data will allow us to
{1} definitively establish the morphological composition and star
formation rates as functions of clustercentric radius, local density,
x-ray luminosity {obtained from accompanying Chandra, and XMM data},
{2} explore the relationship between substructure, kinematics, and
morphology, {3} strongly constrain the galaxy merger frequency and the
origins of elliptical and S0 galaxies, {4} measure the mass
distribution independently from the light {via gravitational lensing}
enabling comparisons with kinematically derived masses, and {5} study
the evolution of the structure of the brightest cluster members. The
clusters selected for this program already have extensive
spectroscopic observations and NIR imaging is either in hand or
underway from approved ground based programs. To date, the lower part
of this redshift range has only been marginally studied with HST. Our
sample includes the two most distant, spectroscopically confirmed
superclusters and will significantly increase the baseline over which
evolutionary effects can be studied. The data will also be used to
identify very high-z galaxies via their unique spectral properties.

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.

ACS/HRC 9853

A Search for Young Binary Brown Dwarfs: Constraining Formation
Scenarios and Masses Through Multiplicity

We propose to use the Advanced Camera for Surveys / High Resolution
Camera to conduct a direct imaging multiplicity survey of 34 young
brown dwarfs in the nearest regions of recent star formation, the T
association Taurus-Auriga and the OB association Upper Scorpius. The
determined multiplicity fraction, the separation distribution, and the
mass ratio distribution will offer stringent observational constraints
on proposed brown dwarf formation scenarios. Moreover, the small
semi-major axes of known field and open cluster brown dwarf binaries
suggest the exciting possibility of our identifying several very close
binaries {< 15 AU}. Continued monitoring of these systems would yield,
on a decade timescale, the first dynamical mass estimates of T Tauri
brown dwarfs. With masses intermediate between those of stars and
planets, brown dwarfs offer our best hope of relating the reasonably
well understood processes of star formation to the less well
understood processes of planet formation.

ACS/WFC 9842

A Snapshot Search for Halo Very-Low-Mass Binaries

We propose a snapshot search for binary M subdwarf stars. These nearby
stars have high velocities and low metallicies that identify them as
members of the old Galactic halo {Population II}. ACS imaging is
requested to search for secondary companions. This supplements a
previous snapshot program that only obtained 10 observations. The
observed binary fraction will be compared to the disk M dwarf fraction
to look for differences in star formation. It is likely that a system
suitable for orbital mass determinations will be found. In this case,
future HST observations could determine the first masses for
very-low-mass, low-metallicity stars.

ACS/HRC 9835

Shooting Stars: Looking for Direct Evidence of Massive Central Black
Holes in Globular Clusters

We propose to make observations that directly test the proposition
that globular clusters contain massive black holes. Our targets are
the bulge globular clusters NGC 6388 and NGC 6441. These are probably
among the most massive in the galaxy, but are understudied compared to
more familiar objects such as M15. Our analysis suggests that these
two clusters are the most likely to show unambiguous evidence for a
central massive black hole if such things exist in globular clusters.
The observations proposed will give us the first thorough kinematic
and photometric studies of these two clusters. The combination of the
two epochs will give us proper motions good to of order 6 km/s. In
addition, they will provide us with the first good, deep,
color-magnitude diagrams for these clusters. These diagrams will be
used to investigate the make up of the stellar population in the
clusters, to more firmly establish their distances, ages, and
metallicities, and to search for a binary sequence.

ACS 9831

Multiplicity among brown dwarfs in the Pleiades cluster

We have compiled a sample of 32 confirmed brown dwarfs in the Pleiades
cluster. We propose to observe this sample with HST/ACS in SNAPSHOT
mode in order to search for very low mass multiple systems. Our goals
are: 1} to determine the occurrence and frequency of binary systems
among substellar objects, which hold important clues to the formation
and evolution mechanism{s} of ultracool and brown dwarfs, 2} to get an
estimate of the Initial Mass Function {IMF} at very low masses, which
is still unknown and very much needed to be corrected for binarity, 3}
to compare the distribution of multiple systems in young open clusters
and in the field.

NIC3/ACS/HRC/WFC 9803

Deep NICMOS Images of the UDF

The ACS Ultra Deep Field {UDF} images will greatly enhance the rich
suite of deep multi-wavelength images in the Chandra Deep Field South
{CDF–S}. We propose to complete the image set with deep near-IR
NICMOS images at 1.1 and 1.6 microns over a significant fraction of
the UDF, providing a critical link between the HST ACS and SIRTF
observations. The timely addition of the near-IR images ensures that
investigators will have images that span the spectrum from X-ray to
far IR. In recognition of the value of the near IR images this
proposal is submitted as a Treasury proposal with no proprietary
period. The proposal team will deliver science quality images,
mosaiced images covering 4.9 sq arc min, and a photometric catalog
complete to an AB mag of 28.2 in both the F110W and F160W filters. The
program also delivers a parallel extremely deep ACS field, 8′ away,
that reaches to within 0.6 mag of the UDF in the same filters as the
UDF. The scientific program of the proposal team focuses on the star
formation history of the universe, evolved galaxies at high redshift,
galaxies at the epoch of reionization, and the redshift evolution of
AGNs and ULIRGs. The HDF-N is currently the only field with
spatially-coincident deep HST imaging in both the optical and near-IR.
The small size of the HDF-N means that large scale structure is the
dominant error in the results from the HDF-N. Providing observations
in a field that is spatially uncorrelated is critically important. The
UDF/CDF-S fulfills that goal. The depth of the UDF ACS imaging, and
the wealth of Great Observatory and ground based observations in the
CDF-S, make these NICMOS observations uniquely valuable. An
extraordinarily rich array of science opportunities await the
community from the NICMOS UDF data.

NIC2 9801

Are OH/IR Stars the Youngest post-AGB stars? A NICMOS Imaging Survey

Essentially all well-characterized preplanetary nebulae {PPNe}–
objects in transition between the AGB and planetary nebula
evolutionary phases – are bipolar, whereas the mass-loss envelopes of
AGB stars are strikingly spherical. In order to understand the
processes leading to bipolar mass-ejection, we need to know at what
stage of stellar evolution does bipolarity in the mass-loss first
manifest itself. We have recently hypothesized that most OH/IR stars
{evolved mass- losing stars with OH maser emission} are very young
PPNe. We are conducting a multiwavelength survey program of imaging
and spectroscopic observations of such objects, using a large,
morphologically unbiased sample selected using IRAS 12-to-25 micron
colors. Our ongoing HST/SNAP imaging survey of the optically bright
half of this sample with WFPC2 and ACS is highly successful: 19/32
objects observed are extended with bipolar/multipolar shapes
{remaining objects are unresolved}. Slightly more than 50% of our
sample are optically too faint or undetected but have strong near-IR
counterparts — we therefore propose a NICMOS SNAPshot imaging survey
of these optically-faint OH/IR stars. These observations are crucial
for determining how and when the bipolar geometry asserts itself. The
results from our NICMOS survey {together with the WFPC2/ACS survey}
will allow us to draw general conclusions about the onset of bipolar
mass-ejection during late stellar evolution. Our complementary program
of interferometric mapping of the OH maser emission in our sources is
yielding kinematic information with spatial resolution comparable to
that in the HST images. The HST/radio data will provide crucial input
for theories of post-AGB stellar evolution. In addition, these data
will also indicate whether the multiple concentric rings, "searchlight
beams”, and truncated equatorial disks recently discovered with HST
in a few PPNe, are common or rare phenomena.

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.

ACS/HRC/WFC 9764

Elliptical galaxies in z~1.5 clusters

Giant elliptical galaxies offer can some of the tightest constraints
on models of galaxy formation. Recent observations have shown
significant inconsistencies between their properties and the
predictions of the currently popular hierarchical clustering models.
Many outstanding questions about the nature and evolution of these
objects can best {or only} be addressed by extending studies of
cluster ellipticals out to z>1. Recently we have identified large
overdensities of red galaxies, strongly clustered around powerful
radio sources at z~1.5. We propose to image our two richest fields, of
Abell Class 0-1 richness, using the F814W and F606W filters on the
ACS/WFC. Our goals are to investigate: {1} Galaxy morphologies: we
will determine the bulge fractions of the red cluster galaxies, to
confirm that they are early-types, and measure their characteristic
radii to investigate their evolutionary status. {2} Colour gradients:
we will search for colour gradients indicative of recent star
formation {particularly blue cores}, or inhomogeneities in the
internal colours which might be indicative of recent assembly. {3}
Cluster membership: with two additional colours we will obtain
accurate photometric redshift estimates for all galaxies. Combined
with studies of nearby clusters and of field ellipticals, our results
will place very tight constraints on the formation of the most massive
galaxies.

ACS/HRC 9747

An Imaging Survey of the Statistical Frequency of Binaries Among
Exceptionally-Young Dynamical Families in the Main Asteroid Belt

We propose an ambitious SNAPSHOT program to determine the frequency of
binaries among two very young asteroid families in the Main Belt, with
potentially profound implications. These families {of C- and S-type}
have recently been discovered {Nesvorny et al. 2002, Nature 417, 720},
through dynamical modeling, to have been formed at 5.8 MY and 8.3 MY
ago in catastrophic impact events. This is the first time such precise
and young ages have been assigned to a family. Main-belt binaries are
almost certainly produced by collisions, and we would expect a young
family to have a significantly higher frequency of binaries than the
background, because they may not yet have been destroyed by impact or
longer-term gravitational instabilities. In fact, one of the prime
observables from such an event should be the propensity for
satellites. This is the best way that new numerical models for binary
production by collisions {motivated largely by our ground-based
discoveries of satellites among larger asteroids}, can be validated
and calibrated. HST is the only facility that can be used to search
for binaries among such faint objects {V>17.5}. We will also measure
two control clusters, one being an "old" family, and the other a
collection of background asteroids that do not have a family
association, and further compare with our determined value for the
frequency of large main-belt binaries {2%}. We request visits to 180
targets, using ACS/HRC.

ACS/WFC 9744

HST Imaging of Gravitational Lenses

Gravitational lenses offer unique opportunities to study cosmology,
dark matter, galactic structure, galaxy evolution and quasar host
galaxies. They are also the only sample of galaxies selected based on
their mass rather than their luminosity or surface brightness. While
gravitational lenses can be discovered with ground-based optical and
radio observations, converting them into astrophysical tools requires
HST. HST has demonstrated that it is the only telescope that can in
each case precisely locate the lens galaxy, measure its luminosity,
color and structure, and search for lensed images of the source host
galaxy given the typical image separations of ~1”. We will obtain
ACS/WFC V and I images and NICMOS H images of 21 new lenses never
observed by HST and NICMOS H images of 16 lenses never observed by HST
in the IR. As in previous cycles, we request that the data be made
public immediately.