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 investigated.)

HSTARS: (None)

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)

                      SCHEDULED  SUCCESSFUL

FGS GSAcq               6                6      

FGS REAcq               6                6      

OBAD with Maneuver 8                8      

SIGNIFICANT EVENTS: (None)

OBSERVATIONS SCHEDULED:

ACS/WFC3 11734

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 z>3 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.

STIS/CCD 11845

CCD Dark Monitor Part 2

Monitor the darks for the STIS CCD.

STIS/CCD 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.

WFC3/IR/S/C 11929

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).

WFC3/UV 12215

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.

WFC3/UV/ACS/WFC 12311

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.

WFC3/UV/IR 12256

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 intriguing object.

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 11914

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.

WFC3/UVIS/IR 11702

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

6.5<z<8.8 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 manner.

(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 ("cosmic

variance").

(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 telescopes.

(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.