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Daily 3724

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Old October 27th 04, 04:43 PM
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Default Daily 3724

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science




ACS/HRC 10332

Starburst Galaxies and Their Population of Super Star Clusters

Starbursts are ideally suited to study the evolution of high mass
stars, the physics of star formation, and the chemical enrichment of
the intergalactic medium {IGM}. Starbursts efficiently form Super Star
Clusters {SSC} which may be young protoglobular clusters. High
resolution imaging will address two important outstanding issues: 1}
how long starbursts last and 2} whether SSCs are indeed young globular
clusters. The duration of starbursts is important because: {1} it
determines how efficiently a starburst can heat and enrich the IGM;
{2} the duration combined with estimates of the fraction of galaxies
which host starbursts yields the total number of starbursts a galaxy
can suffer. Finally, since local starbursts are analogs to high-z
galaxies, the results have implications on the initial formation
timescale of galaxies. Starburst duration will be determined from HRC
imaging of two face-on starburst galaxies rich in SSCs. The UV to
optical colors of the SSCs, which represent single burst chronometers,
will yield their reddening and ages. The range of ages gives the
starburst duration. The nature of SSCs will be investigated by imaging
four of the nearest starbursts in three bands. By comparing the sizes
of their SSCs at different wavelengths we will address the issue of
whether SSCs suffer from early mass segregation. Without some mass
segregation the velocity dispersions of SSCs suggest that they are
deficient in low mass stars, and hence may not represent true
proto-globular clusters.

ACS/HRC 10390

Serendipitous detection of a debris disk near the Sun

We report the unexpected detection of the Fomalhaut debris disk in
scattered light during one orbit of observation for our Cycle 12
program GO9862. This is a major discovery because Fomalhaut is now the
closest {7.7 pc} and oldest {~200 Myr} debris disk detected in
reflected light. We would like to request Director's Discretionary
Time to further study the Fomalhaut disk. The goals are to image the
disk around its entire perimeter, increase the signal-to-noise of the
detection, and to obtain data at a second wavelength. We will perform
a high-resolution study of radial and azimuthal disk asymmetries that
are thought to arise from perturbations by planet-mass companions, and
we will constrain the physical properties of grain material by
obtaining the color of the disk. Because our original Cycle 12 program
was designed to study point sources in the field, and the ACS/HRC
coronagraph is a limited lifetime resource, it is necessary to acquire
these additional data via Director's Discretionary Time during Cycle
13. The observational challenge of high contrast cannot be met by
other observatories, and these data will complement new Spitzer
results on the Fomalhaut disk at mid and far-infrared wavelengths.

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.


The HST survey of the Orion Nebula Cluster

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.

FGS 10202

Resolving OB Binaries in the Carina Nebula, Resuming the Survey

In March 2002 we carried out a small, high-angular resolution survey
of some of the brightest OB stars in the Carina Nebula with FGS1r in
an attempt to resolve binary systems which had thus far evaded
detection by other techniques. Of 23 stars observed, 5 new OB binaries
were discovered with component separations ranging from 0.015"
to0.325". This yield over the spatial domain of FGS1r's angular
resolution, coupled with published statistics of the incidence of OB
stars in short-period spectroscopic, and long-period visual binaries
suggests that the fraction of binarity or multiplicity among OB stars
is near unity. Our unexpected resolution of the prototype O2 If* star
HD 93129A as a 55 milli-arcsecond double is a case in point that great
care must be exercised when one attempts to establish the IMF and
upper-mass cuttoff at the high-mass end of the HR diagram. We propose
to resume the survey to observe a larger, statistically meaningful
sample of OB stars to establish a firm assessment of multiplicity at
the high-mass end of the IMF in these clusters. We will also
investigate the single-star/binary-star status of several
astrophysically important, individual stars in order to enable a
better understanding of the evolution of high-mass stars.

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 10173

Infrared Snapshots of 3CR Radio Galaxies

Radio galaxies are an important class of extragalactic objects: they
are one of the most energetic astrophysical phenomena and they provide
an exceptional probe of the evolving Universe, lying typically in high
density regions but well-represented across a wide redshift range. In
earlier Cycles we carried out extensive HST observations of the 3CR
sources in order to acquire a complete and quantitative inventory of
the structure, contents and evolution of these important objects.
Amongst the results, we discovered new optical jets, dust lanes,
face-on disks with optical jets, and revealed point-like nuclei whose
properties support FR-I/BL Lac unified schemes. Here, we propose to
obtain NICMOS infrared images of 3CR sources with z0.3 as a major
enhancement to an already superb dataset. We aim to deshroud dusty
galaxies, study the underlying host galaxy free from the distorting
effects of dust, locate hidden regions of star formation and establish
the physical characteristics of the dust itself. We will measure
frequency and spectral energy distributions of point-like nuclei,
expected to be stronger and more prevalent in the IR, seek spectral
turnovers in known synchrotron jets and find new jets. We will
strongly test unified AGN schemes and merge these data with existing
X-ray to radio observations. The resulting database will be an
incredibly valuable resource to the astronomical community for years
to come.


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


1274-3 DMS Limits Cleanup @ 300/1627z

FGS Gsacq 14 14
FGS Reacq 03 03
FHST Update 22 22


10 sec non-recoverable 32K HN format Engineering data loss
300/22:34:45-22:34:55z due to WSGT SGLT-4 (TDW) Chain Failover @
300/2235z (Ref. CDS # 37405.)


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