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Daily # 4218



 
 
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Old October 13th 06, 03:43 PM posted to sci.astro.hubble
Joe Cooper
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Default Daily # 4218

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4218

PERIOD COVERED: UT October 12, 2006 (DOY 285)

OBSERVATIONS SCHEDULED

ACS/WFC 10816

The Formation History of Andromeda's Extended Metal-Poor Halo

We propose deep ACS imaging in the outer spheroid of the Andromeda
galaxy, in order to measure the star formation history of its true
halo. For the past 20 years, nearly all studies of the Andromeda
"halo" were focused on the spheroid within 30 kpc of the galaxy's
center, a region now known to host significant substructure and
populations with high metallicity and intermediate ages. However, two
groups have recently discovered an extended metal-poor halo beyond 30
kpc; this population is distinct in its surface-brightness profile,
abundance distribution, and kinematics. In earlier cycles, we obtained
deep images of the inner spheroid {11 kpc on the minor axis}, outer
disk {25 kpc on the major axis}, and giant tidal stream, yielding the
complete star formation history in each field. We now propose deep ACS
imaging of 4 fields bracketing this 30 kpc transition point in the
spheroid, so that the inner spheroid and the extended halo populations
can be disentangled, enabling a reconstruction of the star formation
history in the halo. A wide age distribution in the halo, as found in
the inner spheroid, would imply the halo was assembled through ongoing
accretion of satellite galaxies, while a uniformly old population
would be a strong indication that the halo was formed during the early
rapid collapse of the Andromeda proto-galaxy.

ACS/WFC 10863

Magnifying the High-z Universe with the Bullet Cluster 1E0657-56

We propose to use the bullet cluster 1E0657-56 {z=0.296} as a
gravitational telescope to conduct a pencil beam survey of the galaxy
population to z=7. The cluster 1E0657-56, one of the hottest and most
X-ray luminous clusters known, is a highly efficient lens with
critical curves comparable in size to Abell 1689. The proposed
observations will yield a high-fidelity strong+weak lensing map of the
cluster core, enabling identification of lensed, high-redshift sources
and also providing a precision measurement of the cluster mass {good
to 5% within 350 kpc}. The mass measurement will also serve as a key
input for numerical simulations designed to reconstruct the dynamical
history of the cluster merger and provide a new constraint on the dark
matter self-interaction cross-section. In the cluster core the
requested imaging will reach {de-magnified} magnitudes comparable to
the Hubble Ultra Deep Field for lensed sources, but with 2+ magnitudes
of magnification facilitating spectroscopic follow-up.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration - CR Persistence Part 5

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 10825

The Formation Epoch of Early-type Galaxies: Constraints from the
Fundamental Plane at z=1.3

Field and cluster surveys both show a ~50% decrease in the number of
early-type galaxies at redshifts near 1. Galaxies that have either
recently transformed into early-types or undergone star formation
should have younger appearing stellar populations. The resulting
change in the mass-to-light ratio can be detected by the offset in the
fundamental plane with redshift. We will use the fundamental plane to
test whether a significant fraction of early-type galaxies have
evidence of recent star formation, using a sample of ~20 z=1.3 cluster
and field early-type galaxies. This is 7 times larger than the sample
previously used at this redshift. We already have the high
signal-to-noise 12-20 hour long Keck spectra for these galaxies we
need for velocity dispersions. To use the fundamental plane, we
require sizes and surface brightnesses. We propose 12 orbits of NICMOS
Camera 2 imaging to measure the sizes and surface brightness
distributions of these objects in a rest-frame optical passband. These
data will provide high quality surface brightness profiles out two ~2
half-light radii, at wavelengths comparable to previous fundamental
plane studies. When combined with our spectra, the HST data will
establish the mass-to-light ratio evolution for massive early-type
galaxies from the fundamental plane. We will define the epoch of last
star formation for these z=1.3 galaxies, directly testing the claims
of strong evolution at z=1.

NIC2 11016

NICMOS Flats: narrow and broad filters for NIC1 {+ NIC2, NIC3 in
parallel}

This proposal obtains sequences of NICMOS narrow band filter flat
fields for camera 1. In cameras 2 and 3, parallel observations will
allow us to obtain high S/N flats for all spectral elements.

WFPC2 11028

WFPC2 Cycle 15 UV Earth Flats

Monitor flat field stability. This proposal obtains sequences of earth
streak flats to improve the quality of pipeline flat fields for the
WFPC2 UV filter set. These Earth flats will complement the UV earth
flat data obtained during cycles 8-14.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS: (None)

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSacq 08 08
FGS REacq 07 07
OBAD with Maneuver 28 28

SIGNIFICANT EVENTS: (None)

 




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