Status Report

NASA Hubble Space Telescope Daily Report # 3678

By SpaceRef Editor
August 20, 2004
Filed under , ,

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science




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/HRC 10262

The 3D Morphology of the Extreme Red Supergiant VY Cma

The extreme RSG and powerful OH/IR source VY CMa is surrounded by an
asymmetric reflection nebula dominated by a prominent nebulous arc,
bright filamentary arcs, and several clumps of dusty knots that are
evidence for multiple and asymmetric mass loss events. Our groundbased
velocities show that these structures are kinematically distinct from
the general flow of the diffuse gas and may be directional. We have
speculated that these arcs and knots may be caused by localized
activity on the star involving convection and possibly magnetic fields
analogous to lower mass stars. If correct this would have important
implications for the causes of high mass loss events in evolved
massive stars. Fortunately, VY CMa provides us with an opportunity to
learn more about its possible mass loss mechanisms and history from
the morphology of its ejecta. We propose to use polarimetry and second
epoch images combined with our radial velocities to map the morphology
of the nebula and the discrete structures embedded in it.


CCD Daily Monitor

This program consists of basic tests to monitor, the read noise, the
development of hot pixels and test for any source of noise in ACS CCD
detectors. This programme will be executed once a day for the entire
lifetime of ACS.

ACS/WFC 10325

Low Redshift Cluster Gravitational Lensing Survey

This proposal has two main scientific goals: to determine the dark
matter distribution of massive galaxy clusters, and to observe the
high redshift universe using these clusters as powerful cosmic
telescopes. Deep, g, r, i, z imaging of a sample of low-z {0.2-0.4}
clusters will yield a large sample of lensed background galaxies with
reliable photometric redshifts. By combining strong and weak lensing
constraints with the photometric redshift information it will be
possible to precisely measure the cluster dark matter distribution
with an unprecedented combination of high spatial resolution and area
coverage, avoiding many of the uncertainties which plague ground-based
studies and yielding definitive answers about the structure of massive
dark matter haloes. In addition, the cosmological parameters can be
constrained in a largely model independent way using the multiply
lensed objects due to the dependence of the Einsteinng radius on the
distance to the source. We can also expect to detect several highly
magnified dropout galaxies behind the clusters in the redshift ranges
4-5 5-6 and 7-8, corresponding to a drop in the flux in the g, r, and
i bands relative to longer wavelength. We will obtain the best
information to date on the giant arcs already known in these clusters,
making possible detailed, pixel-by-pixel studies of their star
formation rate, dust distribution and structural components, including
spiral arms, out to a redshift of around z~2.5 in several passbands.


A tailored survey of proplyds with the ACS

While our specific understanding of the proto-planetary disks in Orion
is increasing, our general knowledge of what promotes and hinders
their birth and longevity is hampered by having good observations in
only this one region. Observations of proplyds in other regions with
different conditions of ultraviolet irradiation and age can provide
more stringent tests of our present models. We have therefore designed
an ACS/WFC and parallel WFC2 survey of open clusters embedded in H II
regions that, with a small number of orbits, maximizes the probability
of successfully finding proplyds there. Our observing strategy will
additionally afford a quantitative study of the detected proplyds, as
well as the derivation of a correlation between those characteristics
and the clusters’ stellar population. ACS gives us an unprecedented
opportunity to kick start the mass discovery of proplyds in many
environments, an obvious way in which progress can be made in this
field. This small tailored survey, gives us an excellent chance to
obtain a huge return at low cost.


Stellar Populations in the Outskirts of M33: A Unique Probe of Disk
Galaxy Formation

The fossil record of galaxy formation and evolution is imprinted on
the structure and composition of galactic stellar populations. We have
recently completed an extensive ground-based imaging survey of the low
mass Local Group spiral, M33. Our analysis of the global structure of
M33 suggests it is a ‘pure disk’ galaxy, with no discernible stellar
halo. Furthermore, the disk surface brightness declines very abruptly
beyond ~5 scalelengths. We propose here to obtain deep ACS imagery of
two fields in the far outer disk of M33, located at 4.5 and 6
exponential scalelengths. Deep colour-magnitude diagrams reaching main
sequence turn-offs of ~8 Gyr {corresponding to star formation episodes
since z< 1} will be constructed and used for quantitative modelling of
the star formation history. State-of-the-art cosmological simulations
of galaxy formation predict stars in the outer regions of galactic
disks should be predominantly young-to-intermediate age. The data we
propose to obtain will directly test this idea, and provide a
much-needed observational constraint on the epoch at which disk
galaxies were assembled. The proposed observations will provide an
excellent complement to an ongoing Cycle 11 program to study the outer
disk of the more massive system, M31.

FGS 10108

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 accurately 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.

NIC/NIC3 10226

The NICMOS Grism Parallel Survey

We propose to continue managing the NICMOS pure parallel program.
Based on our experience, we are well prepared to make optimal use of
the parallel opportunities. The improved sensitivity and efficiency of
our observations will substantially increase the number of
line-emitting galaxies detected. As our previous work has
demonstrated, the most frequently detected line is Halpha at
0.7<z<1.9, which provides an excellent measure of current star
formation rate. We will also detect star-forming and active galaxies
in other redshift ranges using other emission lines. The grism
observations will produce by far the best available Halpha luminosity
functions over the crucial–but poorly observed–redshift range where
galaxies appear to have assembled most of their stellar mass. This key
process of galaxy evolution needs to be studied with IR data; we found
that observations at shorter wavelengths appear to have missed a large
fraction of the star-formation in galaxies, due to dust reddening. We
will also obtain deep F110W and F160W images, to examine the space
densities and morphologies of faint red galaxies. In addition to
carrying out the public parallels, we will make the fully reduced and
calibrated images and spectra available on-line, with some
ground-based data for the deepest parallel fields included.

NIC1/NIC2/NIC3 8793

NICMOS Post-SAA calibration – CR Persistence Part 4

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.

NIC2 10176

Coronagraphic Survey for Giant Planets Around Nearby Young Stars

A systematic imaging search for extra-solar Jovian planets is now
possible thanks to recent progress in identifying "young stars near
Earth". For most of the proposed young {<~ 30 Myrs} and nearby {<~ 60
pc} targets, we can detect a few Jupiter-mass planets as close as a
few tens of AUs from the primary stars. This represents the first time
that potential analogs of our solar system – that is planetary systems
with giant planets having semi-major axes comparable to those of the
four giant planets of the Solar System – come within the grasp of
existing instrumentation. Our proposed targets have not been observed
for planets with the Hubble Space Telescope previously. Considering
the very successful earlier NICMOS observations of low mass brown
dwarfs and planetary disks among members of the TW Hydrae Association,
a fair fraction of our targets should also turn out to posses low mass
brown dwarfs, giant planets, or dusty planetary disks because our
targets are similar to {or even better than} the TW Hydrae stars in
terms of youth and proximity to Earth. Should HST time be awarded and
planetary mass candidates be found, proper motion follow-up of
candidate planets will be done with ground-based AOs.

WFPC2 10071

WFPC2 CYCLE 12 Supplemental Darks Part 3/3

This dark calibration program obtains 3 dark frames every day to
provide data for monitoring and characterizing the evolution of hot


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

HSTAR 9520: GS Acquisition (2,1,1) @ 232/09:28:19Z resulted in FL
backup (2,0,2) using FGS 2 due to SSLE on FGS 1. There were no FHST
FM Updates scheduled prior to the primary GS acquisition. Subsequent
FHST Map @ 232/09:36:35Z showed 3-axis (RSS) value ~ 12.00 arcsec.
Under investigation.


17256-0 Genslew for proposal 9862 – slot 4 @ 232/15:22:30z


                         SCHEDULED     SUCCESSFUL    FAILURE TIMES
FGS GSacq              08                       08
FGS REacq              10                       10
FHST Update            12                       12


SpaceRef staff editor.