HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT # 3798
PERIOD COVERED: DOY 46
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/NIC1/WFC 10190
The Star Formation History and Metallicity Evolution of M33: A
Comprehensive Study of Disk Evolution
We will obtain deep, panchromatic imaging photometry of stellar
populations in four fields ranging from 0.5 to 4 scale lengths across
the disk of the Local Group spiral M33. The observations are designed
to detect the oldest main-sequence turnoffs in three outer disk
fields, and to reach the crowding limit in the innermost field. We
will combine the photometry data with information we already have
in-hand on abundances from stars and H II regions in M33 to derive the
star formation history and metallicity evolution of the M33 disk. The
information from our four fields will allow us to obtain {1} the ages
of the oldest disk stars and the radial variation of their ages; {2}
the radial variation of the star formation history and its nature
{e.g., constant, declining, or bursting}; and {3} the metallicity
distribution in each field and the time evolution of the metallicity
gradient. Our team, an experienced mix of photometrists,
spectroscopists, and galaxy evolution theorists, will use the results
from this program to construct a comprehensive chemo- dynamical model
for the M33 disk. This detailed study of M33 will be a key in
developing an understanding of the formation and evolution of disks
that can be applied to studies of disks at both low and high redshift,
and will also yield a wealth of information on stellar populations,
chemical evolution, and star clusters that will be of great value to
future investigators.
ACS/WFC 10188
In-Depth Study of The Antennae with NICMOS and ACS
We propose new observations of "The Antennae" {NGC 4038/39}, the
nearest and youngest example of a major disk-disk merger, with NICMOS
and ACS. The long overdue NICMOS observations will allow us to
penetrate the dust in the Overlap Region, measure the P_alpha emission
and CO band strengths of young clusters, and study supernova remnants
in heavily obscured regions using [FeII] images. The high resolution
{0.05" pixel} ACS observations will allow us for the first time to
reliably distinguish clusters from stars based on their apparent
sizes, and to potentially identify hundreds of supernova remnants that
may control the energy balance and feedback mechanisms within the ISM
{based on [SII] images}. In conjunction with our previous WFPC2, GHRS,
and STIS observations, the new data will provide answers to
fundamental questions such as: How do these clusters form and evolve?
How quickly are they destroyed and what fraction of the field stars
were formed in clusters. How many clusters are hidden by dust? How do
the clusters and associated supernovae affect the local and global
ISM? What are the dynamical masses of the clusters, and are the
stellar IMF's truncated? Simultaneous parallel observations will also
determine whether clusters can form in the more quiescent environment
of the inner tails. A better understanding of how mergers form
tremendous numbers of clusters and stars in the local universe will
help shed light on processes that are crucial during galaxy assembly
throughout the observable universe.
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 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 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.
NIC1/Spacecraft 10382
NICMOS Focus Stability
The purpose of this activity is to determine the best focus. This
program will execute in one month intervals starting about 1 month
after the last execution of proposal 9994 {the previous focus
monitoring program}. The program starts with a focus sweep using only
the NIC1 camera {visit 11}. The following observation is with the NIC2
camera {visit 12} after about 45 days. This pattern is repeated
throughout the period except for Feb 15 where also the NIC3 camera is
used. In total this will result in 9 orbits. Notice that VISIT #1 #2
refers to visits for #1 sequential visit number for a given camera #2
camera in question visit 32 is therefore the third visit for camera 2.
WFPC2 10360
WFPC2 CYCLE 13 INTERNAL MONITOR
This calibration proposal is the Cycle 13 routine internal monitor for
WFPC2, to be run weekly to monitor the health of the cameras. A
variety of internal exposures are obtained in order to provide a
monitor of the integrity of the CCD camera electronics in both bays
{gain 7 and gain 15}, a test for quantum efficiency in the CCDs, and a
monitor for possible buildup of contaminants on the CCD windows.
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: None
SCHEDULED SUCCESSFUL FAILURE TIMES
FGS Gsacq 11 11
FGS Reacq 04 04
FHST Update 20 20
LOSS of LOCK
SIGNIFICANT EVENTS: None
