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Daily Rpt #4576



 
 
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Old March 27th 08, 04:58 PM posted to sci.astro.hubble
Bassford, Lynn
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Posts: 44
Default Daily Rpt #4576

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT # 4576

PERIOD COVERED: UT March 26, 2008 (DOY 086)

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 11213

Distances to Eclipsing M Dwarf Binaries

We propose HST FGS observations to measure accurate distances of 5 nearby M
dwarf eclipsing binary systems, from which model-independent luminosities
can be calculated. These objects have either poor or no existing parallax
measurements. FGS parallax determinations for these systems, with their
existing dynamic masses determined to better than 0.5%, would serve as
model-independent anchor points for the low-mass end of the mass-luminosity
diagram.

NIC1/NIC2/NIC3 11330

NICMOS Cycle 16 Extended Dark

This takes a series of Darks in parallel to other instruments.

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.

NIC2 11219

Active Galactic Nuclei in nearby galaxies: a new view of the origin of
the radio-loud radio-quiet dichotomy?

Using archival HST and Chandra observations of 34 nearby early-type galaxies
{drawn from a complete radio selected sample} we have found evidence that
the radio-loud/radio-quiet dichotomy is directly connected to the structure
of the inner regions of their host galaxies in the following sense: [1]
Radio-loud AGN are associated with galaxies with shallow cores in their
light profiles [2] Radio-quiet AGN are only hosted by galaxies with steep
cusps. Since the brightness profile is determined by the galaxy's evolution,
through its merger history, our results suggest that the same process sets
the AGN flavour. This provides us with a novel tool to explore the
co-evolution of galaxies and supermassive black holes, and it opens a new
path to understand the origin of the radio-loud/radio-quiet AGN dichotomy.
Currently our analysis is statistically incomplete as the brightness profile
is not available for 82 of the 116 targets. Most galaxies were not observed
with HST, while in some cases the study is obstructed by the presence of
dust features. We here propose to perform an infrared NICMOS snapshot survey
of these 82 galaxies. This will enable us to i} test the reality of the
dichotomic behaviour in a substantially larger sample; ii} extend the
comparison between radio-loud and radio-quiet AGN to a larger range of
luminosities.

NIC3 10899

Identifying z7 galaxies from J-dropouts

NICMOS Parallel Imaging campaigns covered enough sky {250 pointings} with
enough sensitivity in the 110W and 160W filters to identify 6 extremely red
resolved sources which are prime candidates for J-band dropouts. Their
complete absence of detectable J band flux can be caused by an opaque Lyman
cut-off at z=8-10. We propose to follow up these candidates with NICMOS
imaging and jointly propose Spitzer IRAC photometry. Deep F110W and
Spitzer/IRAC 3.5/4.8 micron imaging will confirm if any of these candidates
are indeed Lyman Break galaxies observed less than 500 Myrs after the Big
Bang. Genuine LBGs will remain undetected in F110W, while being detected
with flat spectra in the IRAC bands. The combined SED will provide
information about the stellar mass of these galaxies, and the possible
presence of evolved stars or dust reddening. The proposed observations will
be sensitive enough to detect the F110W flux from galaxies as red as
{J-H}=2.8 {AB mags, 5 sigma}. If any of the candidates are detected with
bluer colors, they will most likely be exceptional "Distant Red Galaxies" at
z of 4 to 6. The proposed data will constrain the stellar populations of
these extraordinarily red galaxies, which would be candidates for the
earliest, most massive galaxies which formed.

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.

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 11113

Binaries in the Kuiper Belt: Probes of Solar System Formation and
Evolution

The discovery of binaries in the Kuiper Belt and related small body
populations is powering a revolutionary step forward in the study of this
remote region. Three quarters of the known binaries in the Kuiper Belt have
been discovered with HST, most by our snapshot surveys. The statistics
derived from this work are beginning to yield surprising and unexpected
results. We have found a strong concentration of binaries among
low-inclination Classicals, a possible size cutoff to binaries among the
Centaurs, an apparent preference for nearly equal mass binaries, and a
strong increase in the number of binaries at small separations. We propose
to continue this successful program in Cycle 16; we expect to discover at
least 13 new binary systems, targeted to subgroups where these discoveries
can have the greatest impact.

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!

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 02 02
OBAD with Maneuver 26 26

SIGNIFICANT EVENTS: (None)

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  #2  
Old May 24th 08, 09:37 PM
0523jk 0523jk is offline
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Posts: 8
Default 疏通下水道

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