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Daily Rpt #4438



 
 
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Old September 4th 07, 06:43 PM posted to sci.astro.hubble
Bassford, Lynn
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Posts: 44
Default Daily Rpt #4438

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

DAILY REPORT*** # 4438

PERIOD COVERED: UT August 30, 2007 (DOY 242)

OBSERVATIONS SCHEDULED

FGS 11211

An Astrometric Calibration of Population II Distance Indicators

In 2002 HST produced a highly precise parallax for RR Lyrae. That
measurement resulted in an absolute magnitude, M{V}= 0.61+/-0.11, a
useful result, judged by the over ten refereed citations each year
since. It is, however, unsatisfactory to have the direct,
parallax-based, distance scale of Population II variables based on a
single star. We propose, therefore, to obtain the parallaxes of four
additional RR Lyrae stars and two Population II Cepheids, or W Vir
stars. The Population II Cepheids lie with the RR Lyrae stars on a
common K-band Period-Luminosity relation. Using these parallaxes to
inform that relationship, we anticipate a zero-point error of 0.04
magnitude. This result should greatly strengthen confidence in the
Population II distance scale and increase our understanding of RR
Lyrae star and Pop II Cepheid astrophysics.

FGS 11212

Filling the Period Gap for Massive Binaries

The current census of binaries among the massive O-type stars is
seriously incomplete for systems in the period range from years to
millennia because the radial velocity variations are too small and the
angular separations too close for easy detection. Here we propose to
discover binaries in this observational gap through a Faint Guidance
Sensor SNAP survey of relatively bright targets listed in the Galactic
O Star Catalog. Our primary goal is to determine the binary frequency
among those in the cluster/association, field, and runaway groups. The
results will help us assess the role of binaries in massive star
formation and in the processes that lead to the ejection of massive
stars from their natal clusters. The program will also lead to the
identification of new, close binaries that will be targets of long
term spectroscopic and high angular resolution observations to
determine their masses and distances. The results will also be
important for the interpretation of the spectra of suspected and newly
identified binary and multiple systems.

NIC1/NIC2 11172

Defining Classes of Long Period Variable Stars in M31

We propose a thrifty but information-packed investigation {1440
exposures total} with NICMOS F205W, F160W and F110W providing crucial
information about Long Period Variables in M31, at a level of detail
that has recently allowed the discovery of new variable star classes
in the Magellanic Clouds, a very different stellar population. These
observations are buttressed by an extensive map of the same fields
with ACS and WFPC2 exposures in F555W and F814W, and a massive
ground-based imaging patrol producing well-sampled light curves for
more than 400,000 variable stars. Our primary goal is to collect
sufficient NIR data in order to analyze and classify the huge number
of long-period variables in our catalog {see below} through
Period-Luminosity {P/L} diagrams. We will produce accurate P/L
diagrams for both the bulge and a progression of locations throughout
the disk of M31. These diagrams will be similar in quality to those
currently in the Magellanic Clouds, with their lower metallicity,
radically different star formation history, and larger spread in
distance to the variables. M31 offers an excellent chance to study
more typical disk populations, in a manner which might be extended to
more distant galaxies where such variables are still visible, probing
a much more evenly spread progenitor age distribution than cepheids
{and perhaps useful as a distance scale alternative or cross-check}.
Our data will also provide a massive and unique color- magnitude
dataset, and allow us to confirm the microlensing nature of a large
sample of candidate lensed sources in M31. We expect that this study
will produce several important results, among them a better
understanding of P/L and P/L-color relations for pulsating variables
which are essential to the extragalactic distance ladder, will view
these variables at a common distance over a range of metallicities
{eliminating the distance-error vs. metallicity ambiguity between the
LMC and SMC}, allow further insight into possible faint- variable
mass-loss for higher metallicities, and in general produce a sample
more typical of giant disk galaxies predominant in many studies.

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.

NIC2 11329

The Final SHOE; Completing a Rich Cepheid Field in NGC 1309

The Cycle 15 SHOES program {GO 10802} is a large HST program allocated
186 orbits to rebuild the distance ladder using NGC 4258 as a new
anchor, a set of 6 recent, ideal type Ia supernovae and Cepheids in
their hosts, and NICMOS as a single, homogeneous photometer of long
period Cepheids. These tools provide the means to achieve a 4%
measurement of the Hubble constant, an invaluable constraint for
cosmic concordance fits to dark energy models. Unfortunately, the
SHOES NICMOS integrations of long period Cepheids in the last and most
recent nearby type Ia supernova host, NGC 1309, are too short because
the preliminary estimate of its distance, 30 Mpc, was too low. Our
refined estimate now based on the full reduction of both our Cycle 14
and 15 ACS data is 36 Mpc, or 0.4 mag farther. Fortunately, Nature was
extremely kind providing a single rich NIC2 field in which we can
fully make up for the shortfall due to its abundance of Cepheids. We
are expensing our final 4 orbits on this field of a dozen P30 day
Cepheids and seek an additional 5 orbits to reach the depth for
measuring the mean F160W magnitudes of the long-period Cepheids with
the necessary signal-to-noise ratios of better than 10.

WFPC2 10789

The Role of Environment in the Formation of Dwarf Galaxies

Clusters of galaxies contain an overdensity of dwarfs compared to the
field. Within galaxy clusters there is also a correlation between the
overdensity of dwarfs and local galaxy density, such that areas of
lower galaxy density contain more dwarfs per giant. The origin of
these 'extra' dwarfs is unknown, but a large fraction of them did not
form through standard collapses early in the universe. Some dwarf
ellipticals in clusters have metal rich and young { 6 Gyr} stellar
populations while others contain old metal poor populations,
suggesting multiple formation mechanisms and time scales. We propose
to test the idea that dwarfs descend from galaxies accreted into
clusters during the past 8 Gyr by correlating ages and metallicities
of dwarfs with their internal structures - spiral arms, bars, and
disks. If dwarfs originate from more massive galaxies then these
features should be common in metal rich and young dwarfs. On the other
hand, if no correlation is found it would suggest that dwarfs form
through in-situ collapses of gas in the intragalactic medium after the
universe was reionized.

WFPC2 10915

ACS Nearby Galaxy Survey

Existing HST observations of nearby galaxies comprise a sparse and
highly non-uniform archive, making comprehensive comparative studies
among galaxies essentially impossible. We propose to secure HST's
lasting impact on the study of nearby galaxies by undertaking a
systematic, complete, and carefully crafted imaging survey of ALL
galaxies in the Local Universe outside the Local Group. The resulting
images will allow unprecedented measurements of: {1} the star
formation history {SFH} of a 100 Mpc^3 volume of the Universe with a
time resolution of Delta[log{t}]=0.25; {2} correlations between
spatially resolved SFHs and environment; {3} the structure and
properties of thick disks and stellar halos; and {4} the color
distributions, sizes, and specific frequencies of globular and disk
clusters as a function of galaxy mass and environment. To reach these
goals, we will use a combination of wide-field tiling and pointed deep
imaging to obtain uniform data on all 72 galaxies within a
volume-limited sample extending to ~3.5 Mpc, with an extension to the
M81 group. For each galaxy, the wide-field imaging will cover out to
~1.5 times the optical radius and will reach photometric depths of at
least 2 magnitudes below the tip of the red giant branch throughout
the limits of the survey volume. One additional deep pointing per
galaxy will reach SNR~10 for red clump stars, sufficient to recover
the ancient SFH from the color-magnitude diagram. This proposal will
produce photometric information for ~100 million stars {comparable to
the number in the SDSS survey} and uniform multi- color images of half
a square degree of sky. The resulting archive will establish the
fundamental optical database for nearby galaxies, in preparation for
the shift of high- resolution imaging to the near-infrared.

WFPC2 11039

Polarizers Closeout

Observations of standard stars and a highly polarized reflection
nebula are made as a final calibration for the WFPC2 polarizers.
VISFLATS are also obtained.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10967 - GSacq(2,3,2) failed, Search Radius Limit exceeded on FGS 2

GSacq(2,3,2) at 243/05:47:45 failed at 05:53:54 with search radius
limit exceeded on FGS 2. OBADs prior to GSACQ had RSS errors of
5692.67 and 7.42 arcseconds

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

*************************** SCHEDULED***** SUCCESSFUL
FGS GSacq***************** 10************* 09
FGS REacq***************** 05************* 05
OBAD with Maneuver*** 28************* 28

SIGNIFICANT EVENTS: (None)


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