Status Report

NASA Hubble Space Telescope Daily Report # 3829

By SpaceRef Editor
April 1, 2005
Filed under , ,

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT        # 3829



ACS/HRC 10255

A Never Before Explored Phase Space: Resolving Close White Dwarf / Red
Dwarf Binaries

We propose an ACS Snapshot imaging survey to resolve a well-defined
sample of highly probable white dwarf plus red dwarf close binaries.
These candidates were selected from a search for white dwarfs with
infrared excess from the 2MASS database. They represent unresolved
systems {separations less than approximately 2″ in the 2MASS images}
and are distributed over the whole sky. Our HST+ACS observations will
be sensitive to a separation range {1-20 AU} never before probed by
any means. The proposed study will be the first empirical test of
binary star parameters in the post-AGB phase, and cannot be
accomplished from the ground. By resolving as few as 20 of our ~100
targets with HST, we will be able to characterize the distribution of
orbital semi- major axes and secondary star masses.

ACS/WFC 10174

Dark-matter halos and evolution of high-z early-type galaxies

Gravitational lensing and stellar dynamics provide two complementary
methods to determine the mass distribution and evolution of luminous
and dark-matter in early-type {E/S0} galaxies. The combined study of
stellar dynamics and gravitational lensing allows one to break
degeneracies inherent to each method separately, providing a clean
probe of the internal structure of massive galaxies. Since most lens
galaxies are at redshifts z=0.1-1.0, they also provide the required
look-back time to study their structural and stellar-population
evolution. We recently analyzed 5 E/S0 lens galaxies between z=0.5 and
1.0, combining exquisite Hubble Space Telescope imaging data with
kinematic data from ground-based Keck spectroscopy, placing the first
precise constraints on the dark- matter mass fraction and its inner
slope beyond the local Universe. To expand the sample to ~30 systems
— required to study potential trends and evolution in the E/S0 mass
profiles — we propose to target the 49 E/S0 lens-galaxy candidates
discovered by Bolton et al. {2004} from the Sloan Digital Sky Survey
{SDSS}. With the average lens rate being 40% and some systems having a
lensing probability close to unity, we expect to discover ~20 strong
gravitational lenses from the sample. This will triple the current
sample of 9 E/S0 systems, with data in hand. With the sample of 30
systems, we will be able to determine the average slope of the
dark-matter and total mass profile of E/S0 galaxies to 10% and 4%
accuracy, respectively. If present, we can simultaneously detect 10%
evolution in the total mass slope with 95% confidence. This will
provide unprecedented constraints on E/S0 galaxies beyond the local
Universe and allow a stringent test of their formation scenarios and
the standard cosmological model.

ACS/WFC/NIC/NIC3/WFPC 10246 2 The HST survey of the Orion Nebula

We propose a Treasury Program of 104 HST orbits to perform the
definitive study of the Orion Nebula Cluster, the Rosetta stone of
star formation. We will cover with unprecedented sensitivity {23-25
mag}, dynamic range {~12 mag}, spatial resolution {50mas}, and
simultaneous spectral coverage {5 bands} a ~450 square arcmin field
centered on the Trapezium stars. This represents a tremendous gain
over the shallow WFC1 study made in 1991 with the aberrated HST on an
area ~15 times smaller. We maximize the HST observing efficiency using
ACS/WFC and WFPC2 in parallel with two opposite roll angles, to cover
the same total field. We will assemble the richest, most accurate and
unbiased HR diagram for pre-main-sequence objects ever made. Combined
with the optical spectroscopy already available for ~1000 sources and
new deep near-IR imaging and spectroscopy {that we propose as Joint
HST-NOAO observations}, we will be able to attack and possibly solve
the most compelling questions on stellar evolution: the calibration of
pre-main-sequence evolutionary tracks, mass segration and the
variation of the initial mass function in different environments, the
evolution of mass accretion rates vs. age and environment, disk
dissipation in environments dominated by hard vs. soft-UV radiation,
stellar multiplicity vs. disk fraction. In addition, we expect to
discover and classify an unknown, but substantial, population of
pre-Main Sequence binaries, low mass stars and brown dwarfs down to
~10 MJup. This is also the best possible way to discover dark
silhouette disks in the outskirts of the Orion Nebula and study their
evolutionary status through multicolor imaging. This program is timely
and extremely well leveraged to other programs targeting Orion: the
ACS H-alpha survey of the Orion Nebula, the recently completed 850ks
ultradeep Chandra survey, the large GTO programs to be performed with
SIRTF, plus the availability of 2MASS and various deep JHK surveys of
the core recently done with 8m class telescopes.


The COSMOS 2-Degree ACS Survey

We will undertake a 2 square degree imaging survey {Cosmic Evolution
Survey — COSMOS} with ACS in the I {F814W} band of the VIMOS
equatorial field. This wide field survey is essential to understand
the interplay between Large Scale Structure {LSS} evolution and the
formation of galaxies, dark matter and AGNs and is the one region of
parameter space completely unexplored at present by HST. The
equatorial field was selected for its accessibility to all
ground-based telescopes and low IR background and because it will
eventually contain ~100, 000 galaxy spectra from the VLT-VIMOS
instrument. The imaging will detect over 2 million objects with I> 27
mag {AB, 10 sigma}, over 35, 000 Lyman Break Galaxies {LBGs} and
extremely red galaxies out to z ~ 5. COSMOS is the only HST project
specifically designed to probe the formation and evolution of
structures ranging from galaxies up to Coma-size clusters in the epoch
of peak galaxy, AGN, star and cluster formation {z ~0.5 to 3}. The
size of the largest structures necessitate the 2 degree field. Our
team is committed to the assembly of several public ancillary datasets
including the optical spectra, deep XMM and VLA imaging, ground-based
optical/IR imaging, UV imaging from GALEX and IR data from SIRTF.
Combining the full-spectrum multiwavelength imaging and spectroscopic
coverage with ACS sub-kpc resolution, COSMOS will be Hubble’s ultimate
legacy for understanding the evolution of both the visible and dark


The White Dwarf Cooling Age and Dynamical History of the Metal-Poor
Globular Cluster NGC 6397

We propose to determine the white dwarf cooling age in the nearest
metal-poor {[Fe/H]=- 2} globular cluster, NGC 6397. This globular
cluster provides the best opportunity to test the white dwarf cooling
age in such a metal-poor system and at the same time provide a
comparison with the more metal-rich cluster {M4} which we recently
successfully observed with HST. Any {or even no} age difference
between these clusters will be important in understanding the
age-metallicity relation for these systems which reflects the star
formation history in the early Galaxy. The absolute age is an
important cosmological constraint. We expect to be able to detect age
DIFFERENCES between these clusters at the 0.5 Gyr level and absolute
ages should be accurate to 1.0 Gyr. In addition, and in contrast with
M4, NGC 6397 is highly dynamically evolved, has a collapsed core, and
the distribution of its white dwarfs throughout the cluster have
almost certainly been modified by dynamical processes. We are using
N-body simulations specifically developed for this cluster to
understand these modifications and to include their effects in our
measurement of the white dwarf luminosity function and cooling age.
Among the dynamical questions we expect to answer with this proposal
are: 1} what was the primordial binary frequency in NGC 6397? 2} can
we explain the high central concentration with a population of massive
white dwarfs and/or neutron stars? 3} do we see sufficient central
binaries to reverse the core collapse of the cluster?

FGS 10106

An Astrometric Calibration of the Cepheid Period-Luminosity Relation

We propose to measure the parallaxes of 10 Galactic Cepheid variables.
When these parallaxes {with 1-sigma precisions of 10% or better} are
added to our recent HST FGS parallax determination of delta Cep
{Benedict et al 2002}, we anticipate determining the Period-Luminosity
relation zero point with a 0.03 mag precision. In addition to
permitting the test of assumptions that enter into other Cepheid
distance determination techniques, this calibration will reintroduce
Galactic Cepheids as a fundamental step in the extragalactic distance
scale ladder. A Period-Luminosity relation derived from solar
metallicity Cepheids can be applied directly to extragalactic solar
metallicity Cepheids, removing the need to bridge with the Large
Magellanic Cloud and its associated metallicity complications.

NIC1/NIC2/NIC3 10379

Flats Stability

This calibration proposal is the Cycle 13 NICMOS flat field monitor
program. A series of camera 1, 2, & 3 flat fields will be obtained to
monitor the health of the cameras.

NIC1/NIC2/NIC3 8792

NICMOS Post-SAA calibration – CR Persistence Part 3

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 10337

The COSMOS 2-Degree ACS Survey NICMOS Parallels

The COSMOS 2-Degree ACS Survey NICMOS Parallels. This program is a
companion to program 10092.


Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
investigated.) None


1322-0  Adjust NICMOS FOM Y-AXIS Position Limit @091/1758z

                            SCHEDULED     SUCCESSFUL    FAILURE TIMES 
 FGS Gsacq                 09                       09 
 FGS Reacq                 06                       06 
 FHST Update               15                       15 


SpaceRef staff editor.