Daily Report #5188
HUBBLE SPACE TELESCOPE - Continuing to Collect World Class Science
DAILY REPORT #5188
PERIOD COVERED: 5am September 23 - 5am September 24, 2010 (DOY 266/09:00z-267/09:00z)
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary
reports of potential non-nominal performance that will be
COMPLETED OPS REQUEST:
18924-0 - Genslew for proposal 12312 (slot #1) @ 267/0620z
18925-0 - Genslew for proposal 12312 (slot #2) @ 267/0622z
18926-0 - Genslew for proposal 12312 (slot #3) @ 267/0625z
18927-1 - Genslew for proposal 12312 (slot #4) @ 267/0627z
18928-0 - Genslew for proposal 12312 (slot #5) @ 267/0630z
COMPLETED OPS NOTES: (None)
FGS GSAcq 6 6
FGS REAcq 6 6
OBAD with Maneuver 8 8
SIGNIFICANT EVENTS: (None)
The Hosts of High Redshift Gamma-Ray Bursts
Gamma-ray bursts are the most luminous explosive events known, acting
as beacons to the high redshift universe. Long duration GRBs have
their origin in the collapse of massive stars and thus select star
forming galaxies across a wide range of redshift. Due to their bright
afterglows we can study the details of GRB host galaxies via
absorption spectroscopy, providing redshifts, column densities and
metallicities for galaxies far too faint to be accessible directly
with current technology. We have already obtained deep ground based
observations for many hosts and here propose ACS/WFC3 and WFC3
observations of the fields of bursts at z3 which are undetected in
deep ground based images. These observations will study the hosts in
emission, providing luminosities and morphologies and will enable the
construction of a sample of high-z galaxies with more detailed
physical properties than has ever been possible before.
CCD Dark Monitor Part 2
Monitor the darks for the STIS CCD.
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.
IR Dark Current Monitor
Analyses of ground test data showed that dark current signals are more
reliably removed from science data using darks taken with the same
exposure sequences as the science data, than with a single dark
current image scaled by desired exposure time. Therefore, dark current
images must be collected using all sample sequences that will be used
in science observations. These observations will be used to monitor
changes in the dark current of the WFC3-IR channel on a day-to-day
basis, and to build calibration dark current ramps for each of the
sample sequences to be used by Gos in Cycle 17. For each sample
sequence/array size combination, a median ramp will be created and
delivered to the calibration database system (CDBS).
Searching for the Missing Low-Mass Companions of Massive Stars
Recent results on binary companions of massive O stars appear to
indicate that the distribution of secondary masses is truncated at low
masses. It thus mimics the distribution of companions of G dwarfs and
also the Initial Mass Function (IMF), except that it is shifted upward
by a factor of 20 in mass. These results, if correct, provide a
distribution of mass ratios that hints at a strong constraint on the
star-formation process. However, this intriguing result is derived
from a complex simulation of data which suffer from observational
incompleteness at the low-mass end.
We propose a snapshot survey to test this result in a very direct way.
HST WFC3 images of a sample of the nearest Cepheids (which were
formerly B stars of ~5 Msun) will search for low-mass companions down
to M dwarfs. We will confirm any companions as young stars, and thus
true physical companions, through follow-up Chandra X-ray images. Our
survey will show clearly whether the companion mass distribution is
truncated at low masses, but at a mass much higher than that of the
IMF or G dwarfs.
Multiple Stellar Populations in Galactic Globular Clusters
This is a proposal to bring the unique new properties of WFC3 to bear
on the most exciting recent development in stellar populations:
multiple generations of stars in globular clusters. From our vantage
point in the midst of these developments, we feel that the present-day
situation merits a concentration on increasing the depth of knowledge
in clusters that are already known to have multiple populations,
rather than merely increasing the list of clusters with perplexing
peculiarities. We are therefore proposing to look for a clear
splitting of the main sequence (and other sequences) of 47 Tuc, M4,
M22, NGC 1851, and NGC 6752, and quantify them. The main-sequence
study will cast particular light on the question of helium enrichment.
Coupling the requested F275W data with F814W images available from the
archive will allow us to follow the multiple sequences in the color
magnitude diagram from the main sequence to the horizontal branch and
asymptotic giant branch, and therefore constrain the effects of
enhanced He and CNO on their evolution.
The Ultraviolet and Optical Counterparts of the Intermediate Mass
Black Hole Candidate ESO 243-49 HLX-1
We request imaging observations of the record breaking hyper-luminous
X-ray source and intermediate mass black hole candidate HLX-1 in the
galaxy ESO 243-49, in order to investigate the nature of recent
detections of UV emission and an optical counterpart. HLX-1 is
currently the best candidate for an intermediate mass black hole, the
possible building blocks of super-massive black holes found in the
centres of galaxies. UV emission possibly associated with the X-ray
source position was recently detected in lower resolution observations
with the Swift and GALEX satellites. If this emission can be tied to
HLX-1 and is point-like in nature, it will likely be dominated by
emission from a hot accretion disc. By obtaining UV photometry we will
be able to place constraints upon the temperature of the disc and
therefore the mass of the black hole. The optical counterpart may be
related to disc emission, though it is also possible that it is
associated with a globular cluster or nucleated dwarf galaxy. By
obtaining photometry of the counterpart in near-infrared to UV
wavelengths we will be able to construct a broad-band SED, which will
allow us to place firm constraints on the environment around this
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).
UVIS Earth Flats
This program is an experimental path finder for Cycle 18 calibration.
Visible-wavelength flat fields will be obtained by observing the dark
side of the Earth during periods of full moon illumination. The
observations will consist of full-frame streaked WFC3 UVIS imagery:
per 22- min total exposure time in a single "dark-sky" orbit, we
anticipate collecting 7000 e/pix in F606W or 4500 e/pix in F814W. To
achieve Poisson S/N 100 per pixel, we require at least 2 orbits of
F606W and 3 orbits of F814W.
For UVIS narrowband filters, exposures of 1 sec typically do not
saturate on the sunlit Earth, so we will take sunlit Earth flats for
three of the more-commonly used narrowband filters in Cycle 17 plus
the also-popular long-wavelength quad filters, for which we get four
filters at once.
Why not use the Sunlit Earth for the wideband visible-light filters?
It is too bright in the visible for WFC3 UVIS minimum exposure time of
0.5 sec. Similarly, for NICMOS the sunlit-Earth is too bright which
saturates the detector too quickly and/or induces abnormal behaviors
such as super-shading (Gilmore 1998, NIC 098-011). In the narrowband
visible and broadband near- UV its not too bright (predictions in Cox
et al. 1987 "Standard Astronomical Sources for HST: 6. Spatially Flat
Fields." and observations in ACS Program 10050).
Other possibilities? Cox et al.'s Section II.D addresses many other
possible sources for flat fields, rejecting them for a variety of
reasons. A remaining possibility would be the totally eclipsed moon.
Such eclipses provide approximately 2 hours (1 HST orbit) of
opportunity per year, so they are too rare to be generically useful.
An advantage of the moon over the Earth is that the moon subtends less
than 0.25 square degree, whereas the Earth subtends a steradian or
more, so scattered light and light potentially leaking around the
shutter presents additional problems for the Earth. Also, we're unsure
if HST can point 180 deg from the Sun.
Search for Very High-z Galaxies with WFC3 Pure Parallel
WFC3 will provide an unprecedented probe to the early universe beyond
the current redshift frontier. Here we propose a pure parallel program
using this new instrument to search for Lyman-break galaxies at
6.5z8.8 and to probe the epoch of reionization, a hallmark event in
the history of the early universe. We request 200 orbits, spreading
over 30 ~ 50 high Galactic latitude visits (|b|20deg) that last for 4
orbits and longer, resulting a total survey area of about 140~230
square arcminute. Based on our understanding of the new HST parallel
observation scheduling process, we believe that the total number of
long-duration pure parallel visits in Cycle 17 should be sufficient to
accommodate our program. We waive all proprietary rights to our data,
and will also make the enhanced data products public in a timely
(1) We will use both the UVIS and the IR channels, and do not need to
seek optical data from elsewhere.
(2) Our program will likely triple the size of the probable candidate
samples at z~7 and z~8, and will complement other targeted programs
aiming at the similar redshift range.
(3) Being a pure parallel program, our survey will only make very
limited demand on the scarce HST resources. More importantly, as the
pure parallel pointings will be at random sight-lines, our program
will be least affected by the bias due to the large scale structure
(4) We aim at the most luminous LBG population, and will address the
bright-end of the luminosity function at z~8 and z~7. We will
constrain the value of L* in particular, which is critical for
understanding the star formation process and the stellar mass assembly
history in the first few hundred million years of the universe.
(5) The candidates from our survey, most of which will be the
brightest ones that any surveys would be able to find, will have the
best chance to be spectroscopically confirmed at the current 8--10m
(6) We will also find a large number of extremely red, old galaxies at
intermediate redshifts, and the fine spatial resolution offered by the
WFC3 will enable us constrain their formation history based on the
study of their morphology, and hence shed light on their connection to
the very early galaxies in the universe.
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