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Daily Rpt #4580



 
 
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Old April 2nd 08, 04:01 PM posted to sci.astro.hubble
Bassford, Lynn
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Posts: 44
Default Daily Rpt #4580

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4580

PERIOD COVERED: UT April 01, 2008 (DOY 092)

OBSERVATIONS SCHEDULED

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 11139

NICMOS Observations of the Microquasar GRS 1758-258

The galactic black hole candidate GRS 1758-258 is normally one of the
brightest persistent gamma-ray sources in the vicinity of the galactic
center. It is a microquasar with relativistic radio jets emanating from a
central variable source. Microquasars are excellent nearby test laboratories
for studying the complex accretion and outflow processes that take place
near black hole horizons. Despite an accurate location provided by Chandra
and the VLA and over a decade of careful ground-based studies, the
optical/infrared counterpart to GRS 1758-258 remains unknown. A stellar
counterpart is expected, but the current candidates are all more than 2
sigma from the center of the error circle. The ground-based infrared flux
limits are also right at the values expected for the synchrotron emission
from the outflow from the black hole, and possibly for the emission from the
accretion disk. This leaves open the question as to what is powering this
very energetic persistent source. Here we propose to use NICMOS to perform
broad-band imaging of the GRS 1758- 258 error box. These images will be more
than three magnitudes more sensitive than the current ground-based ones. The
resulting spectra will reveal the thermal/non- thermal nature of the sources
in the region of the error box, and the high spatial resolution images may
reveal a jet structure. We propose to perform three visits of two orbits
each spanning the suggested 18.45 day binary orbital period of the system: a
correct counterpart identification should be confirmed by its variability.
We will also aim to support the HST observations with X- and gamma-ray
observations using Swift or INTEGRAL, and with longer wavelength
observations from the ground.

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration - CR Persistence Part 6

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 i mages. Each observation will need its own CRMAP, as
different SAA passages leave different imprints on the NICMOS detectors.

NIC3 11120

A Paschen-Alpha Study of Massive Stars and the ISM in the Galactic
Center

The Galactic center (GC) is a unique site for a detailed study of a
multitude of complex astrophysical phenomena, which may be common to nuclear
regions of many galaxies. Observable at resolutions unapproachable in other
galaxies, the GC provides an unparalleled opportunity to improve our
understanding of the interrelationships of massive stars, young stellar
clusters, warm and hot ionized gases, molecular clouds, large scale magnetic
fields, and black holes. We propose the first large-scale hydrogen Paschen
alpha line survey of the GC using NICMOS on the Hubble Space Telescope. This
survey will lead to a high resolution and high sensitivity map of the
Paschen alpha line emission in addition to a map of foreground extinction,
made by comparing Paschen alpha to radio emission. This survey of the inner
75 pc of the Galaxy will provide an unprecedented and complete search for
sites of massive star formation. In particular, we will be able to (1)
uncover the distribution of young massive stars in this region, (2) locate
the surfaces of adjacent molecular clouds, (3) determine important physical
parameters of the ionized gas, (4) identify compact and ultra-compact HII
regions throughout the GC. When combined with existing Chandra and Spitzer
surveys as well as a wealth of other multi-wavelength observations, the
results will allow us to address such questions as where and how massive
stars form, how stellar clusters are disrupted, how massive stars shape and
heat the surrounding medium, and how various phases of this medium are
interspersed.

NIC3 11153

The Physical Nature and Age of Lyman Alpha Galaxies

In the simplest scenario, strong Lyman alpha emission from high redshift
galaxies would indicate that stellar populations younger than 10 Myrs
dominate the UV. This does not, however, constrain the stellar populations
older than 100 Myrs, which do not contribute to UV light. Also, the Lyman
alpha line can be boosted if the interstellar medium is both clumpy and
dusty. Different studies with small samples have reached different
conclusions about the presence of dust and old stellar populations in Lyman
alpha emitters. We propose HST- NICMOS and Spitzer-IRAC photometry of 35
Lyman-alpha galaxies at redshift 4.5z6.5, in order to determine their
spectral energy distribution {SED} extending through rest-frame optical.
This will allow us to measure accurately {1} The total stellar mass in these
objects, including old stars which may have formed at redshifts {z 8} not
easily probed by any other means. {2} The dust extinction in the rest-frame
UV, and therefore a correction to their present star-formation rates. Taken
together, these two quantities will yield the star-formation histories of
Lyman alpha galaxies, which form fully half of the known galaxies at z=4-6.
They will tell us whether these are young or old galaxies by straddling the
4000A break. Data from NICMOS is essential for these compact and faint
{i=25-26th magnitude AB} high redshift galaxies, which are too faint for
good near-IR photometry from the ground.

WFPC2 11027

Visible Earth Flats

This proposal monitors flatfield stability. This proposal obtains sequences
of Earth streak flats to construct high quality flat fields for the WFPC2
filter set. These flat fields will allow mapping of the OTA illumination
pattern and will be used in conjunction with previous internal and external
flats to generate new pipeline superflats. These Earth flats will complement
the Earth flat data obtained during cycles 4-14.

WFPC2 11029

WFPC2 CYCLE 15 Intflat Linearity Check and Filter Rotation Anomaly
Monitor

Intflat observations will be taken to provide a linearity check: the
linearity test consists of a series of intflats in F555W, in each gain and
each shutter. A combination of intflats, visflats, and earthflats will be
used to check the repeatability of filter wheel motions. {Intflat sequences
tied to decons, visits 1-18 in prop 10363, have been moved to the cycle 15
decon proposal xxxx for easier scheduling.} Note: long-exposure WFPC2
intflats must be scheduled during ACS anneals to prevent stray light from
the WFPC2 lamps from contaminating long ACS external exposures.

WFPC2 11083

The Structure, Formation and Evolution of Galactic Cores and Nuclei

A surprising result has emerged from the ACS Virgo Cluster Survey {ACSVCS},
a program to obtain ACS/WFC gz imaging for a large, unbiased sample of 100
early-type galaxies in the Virgo Cluster. On subarcsecond scales {i.e.,
0.1"-1"}, the HST brightness profiles vary systematically from the
brightest giants {which have nearly constant surface brightness cores} to
the faintest dwarfs {which have compact stellar nuclei}. Remarkably, the
fraction of galaxy mass contributed by the nuclei in the faint galaxies is
identical to that contributed by supermassive black holes in the bright
galaxies {0.2%}. These findings strongly suggest that a single mechanism is
responsible for both types of Central Massive Object: most likely internally
or externally modulated gas inflows that feed central black holes or lead to
the formation of "nuclear star clusters". Understanding the history of gas
accretion, star formation and chemical enrichment on subarcsecond scales has
thus emerged as the single most pressing question in the study of nearby
galactic nuclei, either active or quiescent. We propose an ambitious HST
program {199 orbits} that constitutes the next, obvious step forward:
high-resolution, ultraviolet {WFPC2/F255W} and infrared {NIC1/F160W} imaging
for the complete ACSVCS sample. By capitalizing on HST's unique ability to
provide high-resolution images with a sharp and stable PSF at UV and IR
wavelengths, we will leverage the existing optical HST data to obtain the
most complete picture currently possible for the history of star formation
and chemical enrichment on these small scales. Equally important, this
program will lead to a significant improvement in the measured structural
parameters and density distributions for the stellar nuclei and the
underlying galaxies, and provide a sensitive measure of "frosting" by young
stars in the galaxy cores. By virtue of its superb image quality and stable
PSF, NICMOS is the sole instrument capable of the IR observations proposed
here. In the case of the WFPC2 observations, high-resolution UV imaging {
0.1"} is a capability unique to HST, yet one that could be lost at any time.

WFPC2 11128

Time Scales Of Bulge Formation In Nearby Galaxies

Traditionally, bulges are thought to fit well into galaxy formation models
of hierarchical merging. However, it is now becoming well established that
many bulges formed through internal, secular evolution of the disk rather
than through mergers. We call these objects pseudobulges. Much is still
unknown about pseudobulges, the most pressing questions being: How, exactly,
do they build up their mass? How long does it take? And, how many exist? We
are after an answer to these questions. If pseudobulges form and evolve over
longer periods than the time between mergers, then a significant population
of pseudobulges is hard to explain within current galaxy formation theories.
A pseudobulge indicates that a galaxy has most likely not undergone a major
merger since the formation of the disk. The ages of pseudobulges give us an
estimate for the time scale of this quiescent evolution. We propose to use
24 orbits of HST time to complete UBVIH imaging on a sample of 33 nearby
galaxies that we have observed with Spitzer in the mid-IR. These data will
be used to measure spatially resolved stellar population parameters {mean
stellar age, metallicity, and star formation history}; comparing ages to
star formation rates allows us to accurately constrain the time scale of
pseudobulge formation. Our sample of bulges includes both pseudo- and
classical bulges, and evenly samples barred and unbarred galaxies. Most of
our sample is imaged, 13 have complete UBVIH coverage; we merely ask to
complete missing observations so that we may construct a uniform sample for
studying bulge formation. We also wish to compare the stellar population
parameters to a variety of bulge and global galaxy properties including star
formation rates, dynamics, internal bulge morphology, structure from
bulge-disk decompositions, and gas content. Much of this data set is already
or is being assembled. This will allow us to derive methods of pseudobulge
identification that can be used to accurately count pseudobulges in large
surveys. Aside from our own science goals, we will present this broad set of
data to the community. Thus, we waive proprietary periods for all
observations.

WFPC2 11198

Pure Parallel Imaging in the NDWFS Bootes Field

The NOAO Deep-Wide Field Survey {NDWFS} Bootes field is the target of one of
the most extensive multiwavelength campaigns in astronomy. In addition to
ground-based optical and near-infrared imaging, deep radio mapping, and
extensive spectroscopy, this entire region has been imaged by the Chandra,
Spitzer {IRAC and MIPS}, and GALEX missions. Robust photometric redshifts
{calibrated using over 20,000 spectroscopic redshifts} exist for all sources
brighter than R=24.5 or than 13 uJy at 4.5 microns. To enhance the value of
this data set, we propose pure parallel observations for all approved Cycle
16 programs in this region that lack coordinated parallel observations. The
primary aim of this program will be to provide a database useful for the
broad range of science programs underway in this region.

WFPC2 11202

The Structure of Early-type Galaxies: 0.1-100 Effective Radii

The structure, formation and evolution of early-type galaxies is still
largely an open problem in cosmology: how does the Universe evolve from
large linear scales dominated by dark matter to the highly non-linear scales
of galaxies, where baryons and dark matter both play important, interacting,
roles? To understand the complex physical processes involved in their
formation scenario, and why they have the tight scaling relations that we
observe today {e.g. the Fundamental Plane}, it is critically important not
only to understand their stellar structure, but also their dark-matter
distribution from the smallest to the largest scales. Over the last three
years the SLACS collaboration has developed a toolbox to tackle these issues
in a unique and encompassing way by combining new non-parametric strong
lensing techniques, stellar dynamics, and most recently weak gravitational
lensing, with high-quality Hubble Space Telescope imaging and VLT/Keck
spectroscopic data of early-type lens systems. This allows us to break
degeneracies that are inherent to each of these techniques separately and
probe the mass structure of early-type galaxies from 0.1 to 100 effective
radii. The large dynamic range to which lensing is sensitive allows us both
to probe the clumpy substructure of these galaxies, as well as their
low-density outer haloes. These methods have convincingly been demonstrated,
by our team, using smaller pilot-samples of SLACS lens systems with HST
data. In this proposal, we request observing time with WFPC2 and NICMOS to
observe 53 strong lens systems from SLACS, to obtain complete multi-color
imaging for each system. This would bring the total number of SLACS lens
systems to 87 with completed HST imaging and effectively doubles the known
number of galaxy-scale strong lenses. The deep HST images enable us to fully
exploit our new techniques, beat down low-number statistics, and probe the
structure and evolution of early-type galaxies, not only with a uniform
data-set an order of magnitude larger than what is available now, but also
with a fully coherent and self-consistent methodological approach!

WFPC2 11326

Polarizers Closeout (Internal Observations)

Verify stability of polarization calibration.

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 11 11
FGS REacq 04 04
OBAD with Maneuver 30 30

SIGNIFICANT EVENTS: (None)

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