Status Report

NASA Hubble Space Telescope Daily Report # 3797

By SpaceRef Editor

February 16, 2005

Filed under Hubble Space Telescope, Space Telescope Science Institute, US

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT # 3797

PERIOD COVERED: DOY 45

OBSERVATIONS SCHEDULED

ACS/HRC 10198

Probing the Dynamics of the Galactic Bar through the Kinematics of
Microlensed Stars

The observed optical depths to microlensing of stars in the Galactic
bulge are difficult to reconcile with our present understanding of
Galactic dynamics. The main source of uncertainty in those comparisons
is now shifting from microlensing measurements to the dynamical models
of the Galactic bar. We propose to constrain the Galactic bar models
with proper motion observations of Bulge stars that underwent
microlensing by determining both the kinematic identity of the
microlensed sources and the importance of streaming motions. The
lensed stars are typically farther than randomly selected stars.
Therefore, our proper motion determinations for 36 targeted MACHO
events will provide valuable constraints on the dynamics of bulge
stars as a function of distance. The first epoch data for our proposed
events is already available in the HST archive so the project can be
completed within a single HST cycle. The exceptional spatial
resolution of HST is essential for completion of the project.
Constraints on the total mass in the bulge will ultimately lead to the
determination of the amount of dark matter in inner Galaxy.

ACS/HRC 10259

Planetary nebulae in the SMC: a study of stellar evolution and
populations in an extremely low-metallicity environment

The final phase of the evolution of low- and intermediate-mass stars,
the planetary nebula {PN} ejection, is thought to largely contribute
to the carbon and nitrogen enrichment in galaxies, in particular in
old stellar populations. Stellar generations forming from a carbon-
and nitrogen-enriched medium are a necessary condition for planetary
and life formation. It is essential to understand how stars go through
the process of shedding their chemically-enriched shells, and to test
the predictions of stellar evolution theory on the relationship
between stellar mass and elemental enrichment. Magellanic Cloud PNs
are ideal probes for this study. Their abundances can be directly
related to the mass of the central stars and to that of the stellar
progenitor, without the great {distance and reddening} uncertainties
that affect Galactic PNs. The UV lines are essential for calculating
the abundances of the element related to stellar evolution {C, N, O}
and to progenitor populations {e.g., Ne}. We propose to acquire UV
spectroscopy of the SMC PNs whose morphology and central star
properties has been previously determined by us with HST. We will
derive the {C, N, O} abundance-to-mass relation, and determine the
extent to which the mass of the progenitors of asymmetric PNs exceed
that of symmetric PNs. We will also test the PN luminosity function,
and probe cosmic recycling, in a very low-metallicity environment.

ACS/HRC/WFC 10367

ACS CCDs daily monitor- cycle 13 – part 1

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.

ACS/WFC 10217

The ACS Fornax Cluster Survey

The two rich clusters nearest to the Milky Way, and the only large
collections of early- type galaxies within ~ 25 Mpc, are the Virgo and
Fornax Clusters. We propose to exploit the exceptional imaging
capabilities of the ACS/WFC to carry out the most comprehensive
imaging survey to date of early-type galaxies in Fornax: the ACS
Fornax Cluster Survey. Deep ACS/WFC images — in the F475W {g’} and
F850LP {z’} bands — will be acquired for 44 E, S0, dE, dE, N and dS0
cluster members. In Cycle 11, we initiated a similar program targeting
early-type galaxies in the Virgo Cluster {the ACS Virgo Cluster
Survey; GO-9401}. Our proposed survey of Fornax would yield an
extraordinary dataset which would complement that already in hand for
Virgo, and allow a definitive study of the role played by environment
in the structure, formation and evolution of early-type galaxies and
their globular cluster systems, nuclei, stellar populations, dust
content, nuclear morphologies and merger histories. It would also be a
community resource for years to come and, together with the ACS Virgo
Cluster Survey, constitute one of the lasting legacies of HST.

ACS/WFC/NIC2 10189

PANS-Probing Acceleration Now with Supernovae

Type Ia supernovae {SNe Ia} provide the most direct evidence for an
accelerating Universe, a result widely attributed to dark energy.
Using HST in Cycle 11 we extended the Hubble diagram with 6 of the 7
highest-redshift SNe Ia known, all at z1.25, providing conclusive
evidence of an earlier epoch of cosmic deceleration. The full sample
of 16 new SNe Ia match the cosmic concordance model and are
inconsistent with a simple model of evolution or dust as alternatives
to dark energy. Understanding dark energy may be the biggest current
challenge to cosmology and particle physics. To understand the nature
of dark energy, we seek to measure its two most fundamental
properties: its evolution {i.e., dw/dz}, and its recent equation of
state {i.e., w{z=0}}. SNe Ia at z1, beyond the reach of the ground
but squarely within the reach of HST with ACS, are crucial to break
the degeneracy in the measurements of these two basic aspects of dark
energy. The SNe Ia we have discovered and measured with HST in Cycle
11, now double the precision of our knowledge of both properties. Here
we propose to quadruple the sample of SNe Ia at z1 in the next two
cycles, complementing on-going surveys from the ground at z<1, and again doubling the precision of dark energy constraints. Should the current best fit model prove to be the correct one, the precision expected from the current proposal will suffice to rule out a cosmological constant at the 99% confidence level. Whatever the result, these objects will provide the basis with which to extend our empirical knowledge of this newly discovered and dominant component of the Universe, and will remain one of the most significant legacies of HST. In addition, our survey and follow-up data will greatly enhance the value of the archival data within the target Treasury fields for galaxy studies.

ACS/WFC/NIC3 10196

Morphologies of a new class of rest-frame optical selected high
redshift galaxies

We have obtained deep very Js, H, Ks imaging with the VLT of two
fields with excellent optical imaging, in order to study high redshift
galaxies. Using these Near-IR images, we identified a class of
galaxies with Js – Ks color larger than 2.3. Photometric redshifts and
spectroscopic follow-up showed that their mean redshift is 2.5 +- 0.7.
These galaxies are complementary to Lyman break selected galaxies: the
overlap is minimal, and the rest-frame optical colors of the Js-Ks
selected galaxies are much redder. Their contribution to the stellar
mass density is comparable to that of Lyman breaks in our fields. SED
fits and Near-IR spectroscopy of the Js-Ks selected galaxies indicate
median ages between 1 and 2 Gyr, a factor of 3-5 older than the ages
of Lyman break galaxies estimated by similar methods. They are likely
the oldest galaxies at z=2.5, and may be evolving into the most
massive galaxies at z=0. We propose to obtain images of the
spectroscopically confirmed Js-Ks galaxies with the NICMOS/NIC3 camera
in the H band. These galaxies lie the field of MS1054-03, for which we
have excellent ground based and HST optical imaging. The increased
depth and spatial resolution of the NICMOS imaging will allow us to
determine the restframe optical morphologies of the Js – Ks galaxies,
in order to study their intensity profiles and regularity, to
decompose the largest galaxies in bulges and disks, to measure scale
lengths, and to look for evidence of merging and recent star
formation. This study would provide us unique insight into the nature
of these red galaxies, their evolutionary history and their likely
descendants at low redshift.

ACS/WFC/WFPC2 10138

Searching for the Bottom of the Initial Mass Function

The minimum mass of the Initial Mass Function {IMF} should be a direct
reflection of the physical processes that dominate in the formation of
stars and brown dwarfs. To date, the IMF has been measured down to 10
M_Jup in a few young clusters; there is no sign of a low-mass cutoff
in the data for these clusters. We propose to obtain deep images in
the SDSS i and z filters {i=26, z=25} with the ACS/WFC on HST for a
800″x1000″ field in the Chamaeleon I star-forming region {2 Myr, 160
pc}. By combining these HST data {0.8, 0.9 um} with comparably deep
broad-band photometry from ground-based telescopes {1.2, 1.6, 2.2 um}
and SIRTF {3.6, 4.5, 5.8, 8.0 um}, we will measure the mass function
of brown dwarfs down to the mass of Jupiter and thus determine the
lowest mass at which objects can form in isolation in a typical star
forming cluster.

FGS 10103

FGS Astrometry of a Star Hosting an Extrasolar Planet: The Mass of
Upsilon Andromedae d

We propose observations with HST/FGS to determine the astrometric
elements {perturbation orbit semimajor axis and inclination} produced
by the outermost extra-solar planet orbiting the F8V star Upsilon
Andromedae. These observations will permit us to determine the actual
mass of the planet by providing the presently unknown sin i factor
intrinsic to the radial velocity method which discovered this object.
An inclination, i = 30degrees, within the range of one very low
precision determination using reanalyzed HIPPARCOS intermediate data
products, would produce the observed radial velocity amplitude, K = 66
ms with a companion mass of ~8 M_Jupiter. Such a mass would induce in
Upsilon Andromedae a perturbation semi-major axis, Alpha = 0arcs0012,
easily within the reach of HST/FGS fringe tracking astrometry. The
proposed observations will yield a planetary mass, rather than, as
previous investigations have done, only suggest a planetary mass
companion.

FGS 10110

Parallaxes of Extreme Halo Subgiants: Calibrating Globular Cluster
Distances and the Ages of the Oldest Stars

The ages of the oldest stars are a key constraint on the evolution of
our Galaxy, the history of star formation, and cosmological models.
These ages are usually determined from globular clusters. However, it
is alternatively possible to determine ages of extreme Population II
subgiants in the solar neighborhood based on trigonometric parallaxes,
without any recourse to clusters. This approach completely avoids the
vexing issues of cluster distances, reddenings, and chemical
compositions. There are 3 known nearby, extremely metal-deficient Pop
II subgiants with Hipparcos parallax errors of 6- 11% which are
available for such age determinations. At present, based on the latest
isochrones, the derived ages of these stars {HD 84937, HD 132475, and
HD 140283} are all close to 14 Gyr, uncomfortably close to or higher
than current estimates of the age of the universe. However, the errors
in the Hipparcos parallaxes imply uncertainties of at least 2 Gyr in
the ages of the 3 stars. We propose to measure parallaxes of these
three Pop II subgiants using HST’s Fine Guidance Sensor 1R. We expect
to reduce the Hipparcos parallax error bars by factors of 5-6,
providing the most stringent test yet of current theoretical stellar
models of Pop II stars and pushing the age uncertainties to below 0.5
Gyr. These data will also provide a major new constraint on the
distance scale of globular clusters, with wide implications for
stellar evolution and the calibration of Pop II standard candles.

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.

NICMOS 8791

NICMOS Post-SAA calibration – CR Persistence Part 2

WFPC2 10359

WFPC2 CYCLE 13 Standard Darks

This dark calibration program obtains dark frames every week in order
to provide data for the ongoing calibration of the CCD dark current
rate, and to monitor and characterize the evolution of hot pixels.
Over an extended period these data will also provide a monitor of
radiation damage to the CCDs.

FLIGHT OPERATIONS SUMMARY:

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

COMPLETED OPS REQs:None

OPS NOTES EXECUTED:
1304-0 HST486 Full RAM Memory Dump @ 045/1552z, 045/1734z
1305-0 HST486 Full EEPROM Memory Dump @ 045/1437z
1306-0 Transfer FSW 2.7A loads & TGS F2G SPC Macro to CMD Queue @ 046/0331z

SCHEDULED SUCCESSFUL FAILURE TIMES FGS Gsacq 07 07 FGS Reacq 07 07 FHST Update 14 14 LOSS of LOCK

SIGNIFICANT EVENTS: None

SpaceRef Editor

SpaceRef staff editor.

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