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Daily Report #5079



 
 
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Old April 21st 10, 03:37 PM posted to sci.astro.hubble
Cooper, Joe
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Default Daily Report #5079

HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #5079

PERIOD COVERED: 5am April 20 - 5am April 21, 2010 (DOY 110/09:00z-111/09:00z)

OBSERVATIONS SCHEDULED

COS/FUV/WFC3/UV/IR/CC/STIS/NUV 11523

COS and WFC3 Observations of I Zwicky 18

We will take advantage of COS' high sensitivity to study both the
stellar and gaseous component (especially HeII 1640 and CIII] 1909),
in I Zwicky 18 (IZw18). We will also take advantage of WFC3's high-QE
IR detector to obtain H-band images of IZw18. The new NIR images will
used in combination with the archival V and I ACS/WFC data to better
characterize the old stellar population, i.e. red giant branch and
asymptotic giant branch stars. The WFC3 observations will be executed
at carefully planned intervals to have a fair sampling in the H band
of the light curve of the Cepheid variable stars already identified in
IZw18.

COS/NUV 11900

NUV Internal/External Wavelength Scale Monitor

This program monitors the offsets between the wavelength scale set by
the internal wavecal versus that defined by absorption lines in
external targets. This is accomplished by observing two external
radial velocity standard targets: HD187691 with G225M and G285M and
HD6655 with G285M and G230L. The two standard targets have little flux
in the wavelength range covered by G185M and so Feige 48 (sdO) is
observed with this grating. Both Feige 48 and HD6655 are also observed
in SMOV. The cenwaves observed in this program are a subset of the
ones used during Cycle 17. Observing all cenwaves would require a
considerably larger number of orbits. Constraints on scheduling of
each target are placed so that each target is observed once every ~2-3
months. Observing the three targets every month would also require a
considerably larger number of orbits.

STIS/CC 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CC 11847

CCD Bias Monitor-Part 2

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 11849

STIS CCD Hot Pixel Annealing

This purpose of this activity is to repair radiation induced hot pixel
damage to the STIS CCD by warming the CCD to the ambient instrument
temperature and annealing radiation-damaged pixels.

Radiation damage creates hot pixels in the STIS CCD Detector. Many of
these hot pixels can be repaired by warming the CCD from its normal
operating temperature near -83 deg. C to the ambient instrument
temperature (~ +5 deg. C) for several hours. The number of hot pixels
repaired is a function of annealing temperature. The effectiveness of
the CCD hot pixel annealing process is assessed by measuring the dark
current behavior before and after annealing and by searching for any
window contamination effects.

WFC3/ACS/IR 11597

Spectroscopy of IR-Selected Galaxy Clusters at 1 z 1.5

We propose to obtain WFC3 G141 and G102 slitless spectroscopy of
galaxy clusters at 1 z 1.5 that were selected from the IRAC survey
of the Bootes NDWFS field. Our IRAC survey contains the largest sample
of spectroscopically confirmed clusters at z 1. The WFC3 grism data
will measure H-alpha to determine SFR, and fit models to the low
resolution continua to determine stellar population histories for the
brighter cluster members, and redshifts for the red galaxies too faint
for ground-based optical spectroscopy.

WFC3/ACS/IR 11600

Star Formation, Extinction, and Metallicity at 0.7z1.5: H-Alpha
Fluxes and Sizes from a Grism Survey of GOODS-N

The global star formation rate (SFR) is ~10x higher at z=1 than today.
This could be due to drastically elevated SFR in some fraction of
galaxies, such as mergers with central bursts, or a higher SFR across
the board. Either means that the conditions in z=1 star forming
galaxies could be quite different from local objects. The next step
beyond measuring the global SFR is to determine the dependence of SFR,
obscuration, metallicity, and size of the star-forming region on
galaxy mass and redshift. However, SFR indicators at z=1 typically
apply local calibrations for UV, [O II] and far-IR, and do not agree
with each other on a galaxy-by-galaxy basis. Extinction, metallicity,
and dust properties cause uncontrolled offsets in SFR calibrations.
The great missing link is Balmer H-alpha, the most sensitive probe of
SFR. We propose a slitless WFC3/G141 IR grism survey of GOODS-N, at 2
orbits/pointing. It will detect Ha+[N II] emission from 0.7z1.5, to
L(Ha) = 1.7 x 10^41 erg/sec at z=1, measuring H-alpha fluxes and sizes
for 600 galaxies, and a small number of higher-redshift emitters.
This will produce: an emission-line redshift survey unbiased by
magnitude and color selection; star formation rates as a function of
galaxy properties, e.g. stellar mass and morphology/mergers measured
by ACS; comparisons of SFRs from H-alpha to UV and far-IR indicators;
calibrations of line ratios of H-alpha to important nebular lines such
as [O II] and H-beta, measuring variations in metallicity and
extinction and their effect on SFR estimates; and the first
measurement of scale lengths of the H-alpha emitting, star- forming
region in a large sample of z~1 sources.

WFC3/ACS/IR 11731

Studying Cepheid Systematics in M81: H-Band Observations

The local value of the Hubble Constant remains one of the most
important constraints in cosmology, but improving on the 10% accuracy
of the HST Key Project is challenging. No improvements will be
convincing until the metallicity dependence is well constrained and
blending effects are fully understood. M81 and its dwarf companion
Holmberg IX are superb laboratories for studying Cepheid systematics
because they contain large numbers of bright Cepheids with a good
spread in metallicity lying at a common, relatively close distance. We
have identified 180 12P 70 day Cepheids in these two galaxies using
the Large Binocular Telescope (compared to 30 in total by the KP), and
will expand the sample further in 2008-2009. We will use 10 orbits
with WFC3/IR to obtain H-band images of 100 Cepheids in M81 to add to
the ACS/BVI calibrations we will obtain from archival data and 1 orbit
with WFC3/UVIS to add B-band data for Holmberg IX. Four band BVIH
photometry will allow us to flux calibrate, estimate extinction,
measure metallicity effects and then check the results in detail. We
can also examine blending effects on WFC3/IR data in a relatively
nearby galaxy before it is applied to more distant galaxies. Our M81
sample is three times larger than the next best sample, that of
NGC4258, and suffers less from blending because M81 is at half the
distance, so it is an excellent laboratory for studying Cepheid
systematics even if it lacks as precise a geometric distance as
NGC4258.

WFC3/ACS/UVIS/COS/NUV/STIS/CCD 11878

HST Post-SM4 and Cycle 17 Focal Plane Calibration

This proposal will determine and monitor the SI positions and
orientations in V2, V3 space. Accuracy goals are 50 mas for position
and between 0.04 and 0.01 degrees for angle (depending on SI). An
astrometric open cluster (M35) is observed using guidestars with
positions determined to ~ 20 mas. One or more astrometric targets are
placed in the available SIs' major channels and POS TARGs can be used
if necessary to step the target(s) over a significant fraction of the
detector. This proposal will serve to update the SI positions and
angles in the SIAF operational database.

WFC3/IR 11719

A Calibration Database for Stellar Models of Asymptotic Giant Branch
Stars

Studies of galaxy formation and evolution rely increasingly on the
interpretation and modeling of near-infrared observations. At these
wavelengths, the brightest stars are intermediate mass asymptotic
giant branch (AGB) stars. These stars can contribute nearly 50% of the
integrated luminosity at near infrared and even optical wavelengths,
particularly for the younger stellar populations characteristic of
high-redshift galaxies (z1). AGB stars are also significant sources
of dust and heavy elements. Accurate modeling of AGB stars is
therefore of the utmost importance.

The primary limitation facing current models is the lack of useful
calibration data. Current models are tuned to match the properties of
the AGB population in the Magellanic Clouds, and thus have only been
calibrated in a very narrow range of sub-solar metallicities.
Preliminary observations already suggest that the models are
overestimating AGB lifetimes by factors of 2-3 at lower metallicities.
At higher (solar) metallicities, there are no appropriate observations
for calibrating the models.

We propose a WFC3/IR SNAP survey of nearby galaxies to create a large
database of AGB populations spanning the full range of metallicities
and star formation histories. Because of their intrinsically red
colors and dusty circumstellar envelopes, tracking the numbers and
bolometric fluxes of AGB stars requires the NIR observations we
propose here. The resulting observations of nearby galaxies with deep
ACS imaging offer the opportunity to obtain large (100-1000's)
complete samples of AGB stars at a single distance, in systems with
well-constrained star formation histories and metallicities.

WFC3/UVIS 11594

A WFC3 Grism Survey for Lyman Limit Absorption at z=2

We propose to conduct a spectroscopic survey of Lyman limit absorbers
at redshifts 1.8 z 2.5, using WFC3 and the G280 grism. This
proposal intends to complete an approved Cycle 15 SNAP program
(10878), which was cut short due to the ACS failure. We have selected
64 quasars at 2.3 z 2.6 from the Sloan Digital Sky Survey
Spectroscopic Quasar Sample, for which no BAL signature is found at
the QSO redshift and no strong metal absorption lines are present at z
2.3 along the lines of sight. The survey has three main

observational goals. First, we will determine the redshift frequency
dn/dz of the LLS over the column density range 16.0 log(NHI) 20.3
cm^-2. Second, we will measure the column density frequency
distribution f(N) for the partial Lyman limit systems (PLLS) over the
column density range 16.0 log(NHI) 17.5 cm^-2. Third, we will
identify those sightlines which could provide a measurement of the
primordial D/H ratio. By carrying out this survey, we can also help
place meaningful constraints on two key quantities of cosmological
relevance. First, we will estimate the amount of metals in the LLS
using the f(N), and ground based observations of metal line
transitions. Second, by determining f(N) of the PLLS, we can constrain
the amplitude of the ionizing UV background at z~2 to a greater
precision. This survey is ideal for a snapshot observing program,
because the on-object integration times are all well below 30 minutes,
and follow-up observations from the ground require minimal telescope
time due to the QSO sample being bright.

WFC3/UVIS 11905

WFC3 UVIS CCD Daily Monitor

The behavior of the WFC3 UVIS CCD will be monitored daily with a set
of full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K
subarray biases are acquired at less frequent intervals throughout the
cycle to support subarray science observations. The internals from
this proposal, along with those from the anneal procedure (Proposal
11909), will be used to generate the necessary superbias and superdark
reference files for the calibration pipeline (CDBS).

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 7 7
FGS REAcq 10 10
OBAD with Maneuver 3 3

SIGNIFICANT EVENTS: (None)


 




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