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Daily Rpt #4415

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Old July 31st 07, 03:41 PM posted to sci.astro.hubble
Bassford, Lynn
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Posts: 44
Default Daily Rpt #4415

Notice: Due to the conversion of some ACS WFC or HRC observations into
WFPC2, or NICMOS observations after the loss of ACS CCD science
capability in January, there may be an occasional discrepancy between
a proposal's listed (and correct) instrument usage and the abstract
that follows it.

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science


PERIOD COVERED: UT July 30, 2007 (DOY 211)


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 DARKs. 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.

WFPC2 11081

RR Lyrae stars in M31 Globular Clusters: How did the M31 Spiral Galaxy

The pulsation properties of the RR Lyrae stars in the globular
clusters of the Andromeda galaxy {M31} have the potential to provide
essential insight on the first epoch of the galaxy formation and to
trace the merging episodes that led to the assembly of M31. Their mean
periods along with the cluster metallicities can provide an
independent estimate of the M31 cluster ages and, in turn, of the time
scale of the M31 halo formation, by comparison with their Milky Way
counterparts. We will observe RR Lyrae stars in 6 appropriately
selected globular clusters of M31 using WFPC2 to derive periods, light
curves, and physical parameters of these eyewitnesses of the first
epochs of the M31 formation.

ACS/SBC 11175

UV Imaging to Determine the Location of Residual Star Formation in
Galaxies Recently Arrived on the Red Sequence

We have identified a sample of low-redshift {z = 0.04 - 0.10} galaxies
that are candidates for recent arrival on the red sequence. They have
red optical colors indicative of old stellar populations, but blue
UV-optical colors that could indicate the presence of a small quantity
of continuing or very recent star formation. However, their spectra
lack the emission lines that characterize star-forming galaxies. We
propose to use ACS/SBC to obtain high-resolution imaging of the UV
flux in these galaxies, in order to determine the spatial distribution
of the last episode of star formation. WFPC2 imaging will provide B,
V, and I photometry to measure the main stellar light distribution of
the galaxy for comparison with the UV imaging, as well as to measure
color gradients and the distribution of interstellar dust. This
detailed morphological information will allow us to investigate the
hypothesis that these galaxies have recently stopped forming stars and
to compare the observed distribution of the last star formation with
predictions for several different mechanisms that may quench star
formation in galaxies.

WFPC2 11292

The Ring Plane Crossings of Uranus in 2007

The rings of Uranus turn edge-on to Earth in May and August 2007. In
between, we will have a rare opportunity to see the unlit face of the
rings. With the nine optically thick rings essentially invisible, we
will observe features and phenomena that are normally lost in their
glare. We will use this opportunity to search thoroughly for the
embedded "shepherd" moons long believed to confine the edges of the
rings, setting a mass limit roughly 10 times smaller than that of the
smallest shepherd currently known, Cordelia. We will measure the
vertical thicknesses of the rings and study the faint dust belts only
known to exist from a single Voyager image. We will also study the
colors of the newly-discovered faint, outer rings; recent evidence
suggests that one ring is red and the other blue, implying that each
ring is dominated by a different set of physical processes. We will
employ near-edge-on photometry from 2006 and 2007 to derive the
particle filling factor within the rings, to observe how ring epsilon
responds to the "traffic jam" as particles pass through its narrowest
point, and to test the latest models for preserving eccentricities and
apse alignment within the rings. Moreover, this data set will allow us
to continue monitoring the motions of the inner moons, which have been
found to show possibly chaotic orbital variations; by nearly doubling
the time span of the existing Hubble astrometry, the details of the
variations will become much clearer.

WFPC2/NIC3 11188

First Resolved Imaging of Escaping Lyman Continuum

The emission from star-forming galaxies appears to be responsible for
reionization of the universe at z6. However, the models that attempt
to describe the detailed impact of high- redshift galaxies on the
surrounding inter-galactic medium {IGM} are strongly dependent upon
several uncertain parameters. Perhaps the most uncertain is the
fraction of HI-ionizing photons produced by young stars which escape
into the IGM. Most attempts to measure this "escape fraction" {f_esc}
have produced null results. Recently, a small subset of z~3 Lyman
Break Galaxies {LBGs} has been found exhibiting large escape
fractions. It remains unclear however, what differentiates them from
other LBGs. Several models attempt to explain how such a large
fraction of ionizing continuum can escape through the HI and dust in
the ISM {eg. "chimneys" created by SNe winds, globular cluster
formation, etc.}, each producing unique signatures which can be
observed with resolved imaging of the escaping Lyman continuum. We
propose a deep, high resolution WFPC2 image of the ionizing continuum
{F336W} and the rest-frame 1500 Angstrom continuum {F606W} of five of
the six known LBGs with large escape fractions. These LBGs all fit
within a single WFPC2 pointing, yielding high observing efficiency.
Additionally, they all have z~3.1 or higher, the optimal redshift
range for probing the Lyman Continuum region with available WFPC2
filters. These factors make our proposed sample especially suitable
for follow- up. With these data we will discern the mechanisms
responsible for producing large escape fractions, and therefore gain
insight into the process of reionization.


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

HSTARS: (None)



************************ SCHEDULED SUCCESSFUL
FGS GSacq******************* 04******** 04
FGS REacq******************* 11******** 11
OBAD with Maneuver***** 30******** 30



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