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Daily Report #5044



 
 
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Old March 3rd 10, 05:54 PM posted to sci.astro.hubble
Cooper, Joe
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Default Daily Report #5044

HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5044

PERIOD COVERED: 5am March 2 - 5am March 3, 2010 (DOY 061/10:00z-062/10:00z)

OBSERVATIONS SCHEDULED

ACS/SBC/COS/NUV/FUV 11579

The Difference Between Neutral- and Ionized-Gas Metal Abundances in
Local Star-Forming Galaxies with COS

The metallicity of galaxies and its evolution with redshift is of
paramount importance for understanding galaxy formation. Abundances in
the interstellar medium (ISM) are typically determined using
emission-line spectroscopy of HII regions. However, since HII regions
are associated with recent SF they may not have abundances typical for
the galaxy as a whole. This is true in particular for star-forming
galaxies (SFGs), in which the bulk of the metals may be contained in
the neutral gas. It is therefore important to directly probe the metal
abundances in the neutral gas. This can be done using absorption lines
in the Far UV. We have developed techniques to do this in SFGs, where
the absorption is measured for sightlines toward bright SF regions
within the galaxy itself. We have successfully applied this technique
to a sample of galaxies observed with FUSE. The results have been very
promising, suggesting in I Zw 18 that abundances in the neutral gas
may be up to 0.5 dex lower than in the ionized gas. However, the
interpretation of the FUSE data is complicated by the very large FUSE
aperture (30 arcsec), the modest S/N, and the limited selection of
species available in the FUSE bandpass. The advent of COS on HST now
allows a significant advance in all of these areas. We will therefore
obtain absorption line spectroscopy with G130M in the same sample for
which we already have crude constraints from FUSE. We will obtain
ACS/SBC images to select the few optimal sightlines to target in each
galaxy. The results will be interpreted through line-profile fitting
to determine the metal abundances constrained by the available lines.
The results will provide important new insights into the metallicities
of galaxies, and into outstanding problems at high redshift such as
the observed offset between the metallicities of Lyman Break Galaxies
and Damped Lyman Alpha systems.

ACS/WFC 11558

Planetary Nebulae, Globular Clusters and Binary Mergers

Four planetary nebulae (PNe) have been found within 130 of the 150
globular clusters (GCs) of our Galaxy. This might not seem like many,
but stellar evolution predicts that the old populations of these
clusters should contain no PN at all! Observations of three of the
four GC PNe show them to have peculiar characteristics, possibly
indicative of a binary/merger origin. In particular two of the three
observed GC PNe have masses which correspond to main sequence masses
~2-3 times the clusters' turn-off masses, suggesting mergers of two,
or even three stars have taken place. One of the three observed PNe is
H-deficient, a characteristic exhibited by only 5 out of hundreds of
field PNe. H-deficient PNe have been associated with binarity. As
usual, not all parameters for these three PNe are clean indications of
their binary origin. In an approved cycle 15 ACS/WFI proposal we asked
to obtain observations of the only GC PN that has never been observed
before at high resolution and whose central star has never been
detected, as well as of the one H-deficient GC PN for which only
low-quality WFPC2 images exist. When ACS stopped working we moved part
of the observations to WFPC2. With this proposal we ask to complete
our project, by obtaining two ACS/WFI images that could not be
efficiently taken with WFPC2. These objects could tip the balance
toward a binary interpretation for the GC PNe or make us seriously
reconsider our understanding of stellar evolution in old populations.

COS/FUV 11895

FUV Detector Dark Monitor

The purpose of this proposal is to monitor the FUV detector dark rate
by taking long science exposures without illuminating the detector.
The detector dark rate and spatial distribution of counts will be
compared to pre-launch and SMOV data in order to verify the nominal
operation of the detector. Variations of count rate as a function of
orbital position will be analyzed to find dependence of dark rate on
proximity to the SAA. Dependence of dark rate as function of time will
also be tracked.

COS/FUV 11897

FUV Spectroscopic Sensitivity Monitoring

The purpose of this proposal is to monitor sensitivity in each FUV
grating mode to detect any changes due to contamination or other
causes.

STIS/CC 11571

A Fundamental Test of Accretion Physics with NGC 4203

The rapid evolution of quasars indicates that supermassive black holes
in galaxy nuclei spend most of their time in a relatively quiescent
state. Studies of nearby galaxies demonstrate that many such black
holes are accreting at a low rate, and appear as low-luminosity active
galactic nuclei (LLAGNs). Theoretical arguments suggest that the mode
of accretion onto a central black hole may be very different in LLAGNs
as compared to high-luminosity systems. The LINER NGC 4203 provides an
excellent opportunity to investigate quantitatively the accretion
process in a LLAGN, and hence the typical accretion state for a
supermassive black hole. Cycle 7 STIS data acquired at one position
angle reveal double-peaked H-alpha emission in the nucleus that may
trace an accretion disk, and spatially resolved emission that places
an upper limit on black-hole mass. We propose observations with STIS
to map the two-dimensional velocity field of the circumnuclear gas
disk in the central regions of NGC 4203, in order to measure the
black-hole mass. This parameter is essential for testing theoretical
models of accretion, determining the mass accretion rate, and
estimating the radiative efficiency for accreted matter. The results
will be important for making sense of LLAGNs, and for translating
their measured luminosity into accretion rates that trace the growth
of black holes. This is a resubmission of a proposal that was approved
for 5 orbits in Cycle 13 (GO-10191) but never carried out due to the
failure of STIS.

STIS/CCD 11844

CCD Dark Monitor Part 1

The purpose of this proposal is to monitor the darks for the STIS CCD.

STIS/CCD 11846

CCD Bias Monitor-Part 1

The purpose of this proposal is to monitor the bias in the 1x1, 1x2,
2x1, and 2x2 bin settings at gain=1, and 1x1 at gain = 4, to build up
high-S/N superbiases and track the evolution of hot columns.

STIS/CCD/MA2 11568

A SNAPSHOT Survey of the Local Interstellar Medium: New NUV
Observations of Stars with Archived FUV Observations

We propose to obtain high-resolution STIS E230H SNAP observations of
MgII and FeII interstellar absorption lines toward stars within 100
parsecs that already have moderate or high-resolution far-UV (FUV),
900-1700 A, observations available in the MAST Archive. Fundamental
properties, such as temperature, turbulence, ionization, abundances,
and depletions of gas in the local interstellar medium (LISM) can be
measured by coupling such observations. Due to the wide spectral range
of STIS, observations to study nearby stars also contain important
data about the LISM embedded within their spectra. However, unlocking
this information from the intrinsically broad and often saturated FUV
absorption lines of low-mass ions, (DI, CII, NI, OI), requires first
understanding the kinematic structure of the gas along the line of
sight. This can be achieved with high resolution spectra of high-mass
ions, (FeII, MgII), which have narrow absorption lines, and can
resolve each individual velocity component (interstellar cloud). By
obtaining short (~10 minute) E230H observations of FeII and MgII, for
stars that already have moderate or high- resolution FUV spectra, we
can increase the sample of LISM measurements, and thereby expand our
knowledge of the physical properties of the gas in our galactic
neighborhood. STIS is the only instrument capable of obtaining the
required high resolution data now or in the foreseeable future.

WFC3/IR 11915

IR Internal Flat Fields

This program is the same as 11433 (SMOV) and depends on the completion
of the IR initial alignment (Program 11425). This version contains
three instances of 37 internal orbits: to be scheduled early, middle,
and near the end of Cycle 17, in order to use the entire 110-orbit
allocation.

In this test, we will study the stability and structure of the IR
channel flat field images through all filter elements in the WFC3-IR
channel. Flats will be monitored, i.e. to capture any temporal trends
in the flat fields and delta flats produced. High signal observations
will provide a map of the pixel-to-pixel flat field structure, as well
as identify the positions of any dust particles.

WFC3/UVIS 11908

Cycle 17: UVIS Bowtie Monitor

Ground testing revealed an intermittent hysteresis type effect in the
UVIS detector (both CCDs) at the level of ~1%, lasting hours to days.
Initially found via an unexpected bowtie-shaped feature in flatfield
ratios, subsequent lab tests on similar e2v devices have since shown
that it is also present as simply an overall offset across the entire
CCD, i.e., a QE offset without any discernable pattern. These lab
tests have further revealed that overexposing the detector to count
levels several times full well fills the traps and effectively
neutralizes the bowtie. Each visit in this proposal acquires a set of
three 3x3 binned internal flatfields: the first unsaturated image will
be used to detect any bowtie, the second, highly exposed image will
neutralize the bowtie if it is present, and the final image will allow
for verification that the bowtie is gone.

WFC3/UVIS 12018

Ultra-Luminous X-Ray Sources in the Most Metal-Poor Galaxies

There is growing observational and theoretical evidence to suggest
that Ultra-Luminous X-ray sources (ULX) form preferentially in low
metallicity environments. Here we propose a survey of 27 nearby (
30Mpc) star-forming Extremely Metal Poor Galaxies (Z5% solar). There
are almost no X-ray observations of such low abundance galaxies (3 in
the Chandra archive). These are the most metal-deficient galaxies
known, and a logical place to find ULX if they favor metal-poor
systems. We plan to test recent population synthesis models which
predict that ULX should be very numerous in metal-poor galaxies. We
will also test the hypothesis that ULX form in massive young star
clusters, and ask for HST time to obtain the necessary imaging data.

WFC3/UVIS/IR 11909

UVIS Hot Pixel Anneal

The on-orbit radiation environment of WFC3 will continually generate
new hot pixels. This proposal performs the procedure required for
repairing those hot pixels in the UVIS CCDs. During an anneal, the
two-stage thermo-electric cooler (TEC) is turned off and the
four-stage TEC is used as a heater to bring the UVIS CCDs up to ~20
deg. C. As a result of the CCD warmup, a majority of the hot pixels
will be fixed; previous instruments such as WFPC2 and ACS have seen
repair rates of about 80%. Internal UVIS exposures are taken before
and after each anneal, to allow an assessment of the procedure's
effectiveness in WFC3, provide a check of bias, global dark current,
and hot pixel levels, as well as support hysteresis (bowtie)
monitoring and CDBS reference file generation. One IR dark is taken
after each anneal, to provide a check of the IR detector.

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 07 07
FGS REAcq 09 09
OBAD with Maneuver 05 05

SIGNIFICANT EVENTS: (None)


 




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