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Daily #4042

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Old February 3rd 06, 02:38 PM posted to sci.astro.hubble
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Default Daily #4042

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science


PERIOD COVERED: UT February 02, 2006 (DOY 033)



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/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 10573

Globular Clusters in the Direction of the Inner Galaxy

The age, chemical and kinematic distributions of stellar populations
provide powerful constraints on models of the formation and evolution
of the Milky Way. The globular clusters constitute an especially
useful case because the stars within individual clusters are coeval
and spatially distinct. But a serious limitation in the study of many
globular clusters -- especially those located near the Galactic Center
-- has been the existence of large absolute and differential
extinction by foreground dust. We propose to use the ACS to map the
differential extinction and remove their effects in a large sample of
globular clusters located in the direction of the inner Galaxy using a
technique refined recently by von Braun and Mateo {2001}. These
observations and their analyses will let us produce high quality
color-magnitude diagrams of these poorly studied clusters that will
allow us to determine these clusters' relative ages, distances and
chemistry and to address important questions about the formation and
the evolution of the inner Galaxy. Our aim for these ACS observations
is to obtain data for the most crowded clusters in the inner Galaxy
where the excellent spatial resolution of the ACS is most necessary.

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/WFC 10596

AGNs with Intermediate-mass Black Holes: A Test of the Black
Hole-Bulge Paradigm

The recent progress in the study of central black holes in galactic
nuclei has led to a general consensus that supermassive {10^6-10^9
solar mass} black holes are closely connected with the formation and
evolutionary history of large galaxies, especially their bulge
component. Two outstanding issues, however, remain unresolved. Can
central black holes form in the absence of a bulge? And does the mass
function of central black holes extend below 10^6 solar masses?
Intermediate-mass black holes {10^4-10^6 solar masses}, if they exist,
may offer important clues to the nature of the seeds of supermassive
black holes. In a first systematic search using the Sloan Digital Sky
Survey, we have recently discovered 19 Type 1 AGNs with candidate
intermediate-mass black holes that reside in low-luminosity,
presumably late-type host galaxies. Follow-up observations with Keck
indicate that these objects obey the low-mass extension of the
well-known correlation between black hole mass and bulge stellar
velocity dispersion. However, very little is known about the host
galaxies themselves, including the crucial question of whether they
have bulges or not. We propose to obtain ACS/WFC images of this unique
sample of AGNs in order to investigate the detailed structural
properties of the host galaxies. We are particularly keen to determine
whether the hosts contain bulges, and if so, where they lie on the
fundamental plane of spheroids compared to the bulges of supermassive
black holes. We will also be able to measure an accurate optical
luminosity for the AGN, which is an essential ingredient to improve
the current mass estimates.


Probing Evolution And Reionization Spectroscopically {PEARS}

While imaging with HST has gone deep enough to probe the highest
redshifts, e.g. the GOODS survey and the Ultra Deep Field,
spectroscopic identifications have not kept up. We propose an ACS
grism survey to get slitless spectra of all sources in a wide survey
region {8 ACS fields} up to z =27.0 magnitude, and an ultradeep field
in the HUDF reaching sources up to z =28 magnitude. The PEARS survey
will: {1} Find and spectrocopically confirm all galaxies between
z=4-7. {2} Probe the reionization epoch by robustly determining the
luminosity function of galaxies and low luminosity AGNs at z = 4 - 6.
With known redshifts, we can get a local measure of star formation and
ionization rate in case reionization is inhomogeneous. {3} Study
galaxy formation and evolution by finding galaxies in a contiguous
redshift range between 4 z 7, and black hole evolution through a
census of low-luminosity AGNs. {4} Get a robust census of galaxies
with old stellar populations at 1 z 2.5, invaluable for checking
consistency with heirarchical models of galaxy formation. Fitting
these galaxies' spectra will yield age and metallicity estimates. {5}
Study star-formation and galaxy assembly at its peak at 1 z 2 by
identifying emission lines in star-forming galaxies, old populations
showing the 4000A break, and any combination of the two. {6} Constrain
faint white dwarfs in the Galactic halo and thus measure their
contribution to the dark matter halo. {7} Derive spectro-photometric
redshifts by using the grism spectra along with broadband data. This
will be the deepest unbiased spectroscopy yet, and will enhance the
value of the multiwavelength data in UDF and the GOODS fields to the
astronomical community. To this end we will deliver reduced spectra to
the HST archives.


The Formation of Spiral Spheroids and Their Globular Cluster Systems

The assembly history of spiral galaxies remains one of the most
pressing questions in astrophysics today. In particular, we do not
have a clear picture of the formation mechanism for bulges of spiral
galaxies. Are bulges of spirals simply "small ellipticals", formed via
rapid dissipative collapse during the early universe? Or is bulge
building through secular evolution of inner disk stars a more common
mechanism? Is there any dependence on bulge mass? A powerful yet
relatively simple way to probe these fundamental questions is by
studying the properties of globular cluster {GC} systems of spirals.
Specifically, bulge formation via secular evolution is expected not to
form GCs, whereas bulge formation via dissipative collapse is. We
therefore propose to obtain ACS/WFC imaging as well as ground-based,
wide-field imaging of five edge-on Sa spirals which cover a factor ~15
in luminosity/mass, and for which spectroscopic follow-up is feasible.
This constitutes the first luminosity-selected sample of early-type
spirals, which will allow us to directly probe the dependence of GC
properties on the bulge luminosity. We will detect a minimum of
~100-200 GCs per galaxy in the ACS images, sufficient to reveal GC
subpopulations, their relative numbers, sizes, and radial
distributions. This study will more than double the number of
well-studied early-type spiral systems.

FGS 10478

Dynamical Masses and Radii of Four White Dwarf Stars

The cool white dwarf stars WD1639+153 and WD1818+126 were recently
resolved by HST FGS1r to be double degenerate binary systems with
projected separations of 112 mas and 174 mas respectively. At a
distance of less than 50 pc they may both have periods shorter than
about 20 years, making them ideal candidates for follow up studies for
dynamical mass determinations. This will increase the number of white
dwarfs with dynamical mass measurements from the current 4 up to 8.
Continued observations of these white dwarfs along with nearby field
stars with the FGS will accuractely determine the orbital elements and
parallax of each system. The mass and radius of all four white dwarfs
can be determined to an unprecedented 1%, making it possible to test
and calibrate the theoretical white dwarf mass radius relation at the
cool end of the cooling curve for the DA and DC subclasses. Since the
components of the binary are coeval, once the mass and radius, and
hence the cooling age of each star is known, it will be possible to
estimate the relation between the initial mass and final mass for all
four white dwarfs. We are requesting a total of 4 HST orbits per year
for the next three cycles to initiate the process that will result in
a determination of the mass and radius of the four white dwarfs.

FGS 10610

Astrometric Masses of Extrasolar Planets and Brown Dwarfs

We propose observations with HST/FGS to estimate the astrometric
elements {perturbation orbit semi-major axis and inclination} of
extra-solar planets orbiting six stars. These companions were
originally detected by radial velocity techniques. We have
demonstrated that FGS astrometry of even a short segment of reflex
motion, when combined with extensive radial velocity information, can
yield useful inclination information {McArthur et al. 2004}, allowing
us to determine companion masses. Extrasolar planet masses assist in
two ongoing research frontiers. First, they provide useful boundary
conditions for models of planetary formation and evolution of
planetary systems. Second, knowing that a star in fact has a plantary
mass companion, increases the value of that system to future
extrasolar planet observation missions such as SIM PlanetQuest, TPF,
and GAIA.


NICMOS Post-SAA calibration - CR Persistence Part 2

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.


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

HSTARS: (None)



FGS GSacq 13 13
FGS REacq 02 02
OBAD with Maneuver 30 30



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