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Daily Rpt #4995



 
 
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Old December 18th 09, 07:43 PM posted to sci.astro.hubble
Bassford, Lynn[_2_]
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Posts: 91
Default Daily Rpt #4995

HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science

DAILY REPORT #4995

PERIOD COVERED: 5am December 17 - 5am December 18, 2009 (DOY 351/10:00z-352/10:00z)

OBSERVATIONS SCHEDULED

COS/FUV 11625

Beyond the Classical Paradigm of Stellar Winds: Investigating Clumping,
Rotation and the Weak Wind Problem in SMC O Stars

SMC O stars provide an unrivaled opportunity to probe star formation,
evolution, and the feedback of massive stars in an environment similar
to the epoch of the peak in star formation history. Two recent
breakthroughs in the study of hot, massive stars have important
consequences for understanding the chemical enrichment and buildup of
stellar mass in the Universe. The first is the realization that
rotation plays a major role in influencing the evolution of massive
stars and their feedback on the surrounding environment. The second is
a drastic downward revision of the mass loss rates of massive stars
coming from an improved description of their winds. STIS spectroscopy
of SMC O stars combined with state-of-the-art NLTE analyses has shed
new light on these two topics. A majority of SMC O stars reveal
CNO-cycle processed material brought at their surface by rotational
mixing. Secondly, the FUV wind lines of early O stars provide strong
indications of the clumped nature of their wind. Moreover, we first
drew attention to some late-O dwarfs showing extremely weak wind
signatures. Consequently, we have derived mass loss rates from STIS
spectroscopy that are significantly lower than the current theoretical
predictions used in evolutionary models. Because of the limited size
of the current sample (and some clear bias toward stars with
sharp-lined spectra), these results must however be viewed as
tentative. Thanks to the high efficiency of COS in the FUV range, we
propose now to obtain high-resolution FUV spectra with COS of a larger
sample of SMC O stars to study systematically rotation and wind
properties of massive stars at low metallicity. The analysis of the
FUV wind lines will be based on our 2D extension of CMFGEN to model
axi-symmetric rotating winds.

COS/NUV/FUV 11528

COS-GTO: Studies of the He II Reionization Epoch

Intergalactic Ly-alpha opacity suggests that H I was reionized at z ~
6, while He II reionization was delayed to z ~ 3. Both epochs are
slightly in disagreement with recent (WMAP-3) inferences from the CMB
optical depth, which suggest that IGM reionization occurred at z =
10.7 (+2.7, -2.3) (Spergel et al. 2007). However, these two methods
are sensitive to different ranges of ionization (neutral fractions),
which allows a partially ionized IGM between z = 6-10 produced by
early stars and black holes. One of the major contributions of FUSE to
cosmological studies was the detection of He II Ly-alpha
(Gunn-Peterson) absorption in the spectra of two AGN at redshifts z =
2.72-2.89. The He II absorption is quite patchy between redshifts z =
2.6 and 3.2 probably because the IGM is clumpy and the reionization
process is affected by source fluctuations, spectra, and radiative
transfer through the IGM. Observations of the He II absorption can
therefore be used as diagnostics of the ionizing sources and radiative
transport over large (30-50 Mpc) distances through the IGM. The
ionizing radiation field appears to be softer (higher He II/H I) in
the galaxy voids. These void regions may be ionized by local soft
sources (dwarf starburst galaxies), or the QSO radiation may softened
by escape from AGN cores and transport through denser regions in the
cosmic web. With COS, we will observe the brightest He II target,
HE2347-4342, a QSO with z_em = 2.885. Our goal is to obtain a G130M
moderate-resolution (R = 20, 000) spectrum from 1145-1450A. Because
COS has far greater throughput than either STIS or FUSE, we will be
able to resolve and characterize the He II absorption lines. The
region shortward of the redshifted He II (Ly-alpha) corresponds to z =
2.77-2.92, where He II exhibits patchy transmission and absorption.
The ratio of He II/H I (Ly-alpha line) opacities will provide
information on the ionizing radiation field (and ionizing sources) at
1 and 4 ryd. We will perform similar He II studies on three other
targets, HS1700+6416, PKS1935-692, and Q0302-003.

COS/NUV/FUV/STIS/CCD/MA1 11692

The LMC as a QSO Absorption Line System

We propose to obtain high resolution, high signal-to-noise
observations of QSOs behind the Large Magellanic Clouds. These QSOs
are situated beyond the star forming disk of the galaxy, giving us the
opportunity to study the distribution of metals and energy in regions
lacking significant star formation. In particular, we will derive the
metallicities and study the ionization characteristics of LMC gas at
impact parameters 3-17 kpc. We will compare our results with high-z
QSO absorption line systems.

NIC3/WFC3/IR 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.

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.

WFC3/ACS/UVIS/IR 11570

Narrowing in on the Hubble Constant and Dark Energy

A measurement of the Hubble constant to a precision of a few percent
would be a powerful aid to the investigation of the nature of dark
energy and a potent "end-to end" test of the present cosmological
model. In Cycle 15 we constructed a new streamlined distance ladder
utilizing high-quality type Ia supernova data and observations of
Cepheids with HST in the near-IR to minimize the dominant sources of
systematic uncertainty in past measurements of the Hubble constant and
reduce its total uncertainty to a little under 5%. Here we propose to
exploit this new route to reduce the remaining uncertainty by more
than 30%, translating into an equal reduction in the uncertainty of
the equation of state of dark energy. We propose three sets of
observations to reach this goal: a mosaic of NGC 4258 with WFC3 in
F160W to triple its sample of long period Cepheids, WFC3/F160W
observations of the 6 ideal SN Ia hosts to triple their samples of
Cepheids, and observations of NGC 5584 the host of a new SN Ia, SN
2007af, to discover and measure its Cepheids and begin expanding the
small set of SN Ia luminosity calibrations. These observations would
provide the bulk of a coordinated program aimed at making the
measurement of the Hubble constant one of the leading constraints on
dark energy.

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 11643

A Timeline for Early-Type Galaxy Formation: Mapping the Evolution of
Star Formation, Globular Clusters, Dust, and Black Holes

While considerable effort has been devoted to statistical studies of
the origin of the red sequence of galaxies, there has been relatively
little direct exploration of galaxies transforming from late to early
types. Such galaxies are identified by their post-starburst spectra,
bulge-dominated, tidally-disturbed morphologies, and current lack of
gas. We are constructing the first detailed timeline of their
evolution onto the red sequence, pinpointing when star formation ends,
nuclear activity ceases, globular clusters form, and the bulk of the
merging progenitors' dust disappears. Here we propose to obtain HST
and Chandra imaging of nine galaxies, whose wide range of
post-starburst ages we have precisely dated with a new UV-optical
technique and for which we were awarded Spitzer time. We will address
1) whether the black hole-bulge mass relation arises from nuclear
feedback, 2) whether the bimodality of globular cluster colors is due
to young clusters produced in galaxy mergers, and 3) what happens to
the dust when late types merge to form an early type.

WFC3/UVIS 11714

Snapshot Survey for Planetary Nebulae in Local Group Globular Clusters

Planetary nebulae (PNe) in globular clusters (GCs) raise a number of
interesting issues related to stellar and galactic evolution. The
number of PNe known in Milky Way GCs, four, is surprisingly low if one
assumes that all stars pass through a PN stage. However, it is likely
that the remnants of stars now evolving in galactic GCs leave the AGB
so slowly that any ejected nebula dissipates long before the star
becomes hot enough to ionize it. Thus there should not be ANY PNe in
Milky Way GCs--but there are four! It has been suggested that these
Pne are the result of mergers of binary stars within GCs, i.e., that
they are descendants of blue stragglers. The frequency of occurrence
of PNe in external galaxies poses more questions, because it shows a
range of almost an order of magnitude.

I propose a SNAPshot survey aimed at discovering PNe in the GC systems
of Local Group galaxies outside the Milky Way. These clusters, some of
which may be much younger than their counterparts in our galaxy, might
contain many more PNe than those of our own galaxy. I will use the
standard technique of emission-line and continuum imaging, which
easily discloses PNe. This proposal continues a WFPC2 program started
in Cycle 16, but with the more powerful WFC3. As a by-product, the
survey will also produce color-magnitude diagrams for numerous
clusters for the first time, reaching down to the horizontal branch.

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).

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 11912

UVIS Internal Flats

This proposal will be used to assess the stability of the flat field
structure for the UVIS detector throughout the 15 months of Cycle 17.
The data will be used to generate on- orbit updates for the delta-flat
field reference files used in the WFC3 calibration pipeline, if
significant changes in the flat structure are seen.

WFC3/UVIS/IR 11700

Bright Galaxies at z7.5 with a WFC3 Pure Parallel Survey

The epoch of reionization represents a special moment in the history
of the Universe as it is during this era that the first galaxies and
star clusters are formed. Reionization also profoundly affects the
environment where subsequent generations of galaxies evolve. Our
overarching goal is to test the hypothesis that galaxies are
responsible for reionizing neutral hydrogen. To do so we propose to
carry out a pure parallel WFC3 survey to constrain the bright end of
the redshift z7.5 galaxy luminosity function on a total area of 176
arcmin^2 of sky. Extrapolating the evolution of the luminosity
function from z~6, we expect to detect about 20 Lyman Break Galaxies
brighter than M_* at z~8 significantly improving the current sample of
only a few galaxies known at these redshifts. Finding significantly
fewer objects than predicted on the basis of extrapolation from z=6
would set strong limits to the brightness of M_*, highlighting a fast
evolution of the luminosity function with the possible implication
that galaxies alone cannot reionize the Universe. Our observations
will find the best candidates for spectroscopic confirmation, that is
bright z7.5 objects, which would be missed by small area deeper
surveys. The random pointing nature of the program is ideal to beat
cosmic variance, especially severe for luminous massive galaxies,
which are strongly clustered. In fact our survey geometry of 38
independent fields will constrain the luminosity function like a
contiguous single field survey with two times more area at the same
depth. Lyman Break Galaxies at z7.5 down to m_AB=26.85 (5 sigma) in
F125W will be selected as F098M dropouts, using three to five orbits
visits that include a total of four filters (F606W, F098M, F125W,
F160W) optimized to remove low-redshift interlopers and cool stars.
Our data will be highly complementary to a deep field search for
high-z galaxies aimed at probing the faint end of the luminosity
function, allowing us to disentangle the degeneracy between faint end
slope and M_* in a Schechter function fit of the luminosity function.
We waive proprietary rights for the data. In addition, we commit to
release the coordinates and properties of our z7.5 candidates within
one month from the acquisition of each field.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

#12134 REAcq(1,2,1) @351/10:25z failed to gyro control

Observation affected: WFC3 #90-95 Proposal #11643.

#12135 GSAcq(1,2,1) @351/13:02z & REAcq(1,2,1) @ 351/14:05z, 15:41z &
17:17z failed due to search radius limit exceeded

Observations affected: COS #89-93 Proposal# 11692; WFC3 #100-104
Proposal# 11700

#12136 GSAcq(2,3,3) @352/02:26:03z, REAcq(2,3,3) @352/04:02:17z &
REAcq(2,3,3) @352/07:14:00z failed to gyro control with search radius
limit exceeded on FGS-2

REAcq(2,3,3) @352/05:38:09z was successful in acquiring fine lock on
both FGS 2 and 3.

Observations affected: COS #94-96 & #98 Proposal #11727; WFC3 #120-126
& #131-132 Proposal #11696

#12137 GSAcq(2,1,1) @352/09:19:33z acquires with fine lock backup on
FGS 1 and scan step limit exceeded on FGS 2 @352/09:23:05z

FGS 2 acquired and lost lock twice between 352/09:22:54 and 09:24:46

Observation possibly affected: WFC3 #135 Proposal #11208.

COMPLETED OPS REQUEST:

#18568-1 LBBIAS Updates for Extended Gyro Guiding Intervals (Generic)
@351/11:24z, 351/14:25z, 351/15:58z, 351/17:16z, 352/03:29z,
352/06:40z
#18787-0 LBBIAS Gyro Bias Update @351/10:52z
#18789-0 LBBIAS Gyro Bias Update @351/17:04z

COMPLETED OPS NOTES: (None)

SCHEDULED SUCCESSFUL
FGS GSAcq 8 6
FGS REAcq 7 1
OBAD with Maneuver 4 4
LOSS of LOCK 1

SIGNIFICANT EVENTS:

2nd Gyro 3 Reconfiguration to Backup Heater:

The Gyro 3 heater controller was switched to the backup controller at
350/21:45. Initial biases measurements up to 351/01:50 were nominal,
however the GS acquisition at 351/02:57 failed to Loss of Lock (LOL)
looping which is indicative of a bias issue. Subsequent biases
appeared to increase in the V2 and V3 axes and acquisitions between
06:07 and 10:27 failed due to search radius limit exceeds (SRLEX) or
LOL looping while efforts were made to correct the bias. The GS
acquisition at 12:01 was successful and performed an onboard bias
update. The GS acquisition at 13:05 failed due to a dim star and
another full acquisition will not occur until 19:01. Another LBBIAS
update is in work to correct the bias.
 




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