HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT      #4773

PERIOD COVERED: 5am January 15 - 5am January 16, 2009 (DOY

                           015/1000z-016/1000z)

OBSERVATIONS SCHEDULED

ASC/SBC 11236

Did Rare, Large Escape-Fraction Galaxies Reionize the Universe?

Lyman continuum photons produced in massive starbursts may have played a

dominant role in the reionization of the Universe. Starbursts are

important contributors to the ionizing metagalactic background at lower

redshifts as well. However, their contribution to the background depends

upon the fraction of ionizing radiation that escapes from the intrinsic

opacity of galaxies below the Lyman limit. Current surveys suggest that

the escape fraction is close to zero in most galaxies, even among young

starbursts, but is large in 15-25% of them. Non-uniform escape fractions

are expected as a result of violent events creating clear paths in small

parts of galaxies. The number of galaxies observed with high escape

fraction will result from the combination of the intrinsic number with

clear lines of sight and their orientation with respect to the observer.

We propose to measure the fraction of escaping Lyman continuum radiation

in a large sample (47) of z~0.7 starbursts in the COSMOS field. These

compact UV-luminous galaxies are good analogs to high redshift LBGs.

Using the SBC/PR130L we can quickly (1-4 orbits) detect relative escape

fractions (f_LC/f_1500) of 25% or more. This will be the first

measurement of the escape fraction in sources between z=1 and the local

universe. We expect ~10 detections. Stacking will set limits of <4% on

the relative escape fraction in the rest. We will correlate the LC

detections with the properties of the galaxies. By targeting z~0.7 in

COSMOS, we will have tremendous ancillary information on those sources.

A non-detection in all sources would be significant (99% confidence).

This would imply that QSOs provide the overwhelming majority of ionizing

radiation at z<1, requiring substantial evolution in the processes

within Lyman break galaxies which allow large escape fractions at high

redshift.

WFPC2 11944

Binaries at the Extremes of the H-R Diagram

We propose to use HST/Fine Guidance Sensor 1r to survey for binaries

among some of the most massive, least massive, and oldest stars in our

part of the Galaxy. FGS allows us to spatially resolve binary systems

that are too faint to observe using ground-based, speckle or optical

long baseline interferometry, and too close to resolve with AO. We

propose a SNAP-style program of single orbit FGS TRANS mode observations

of very massive stars in the cluster NGC 3603, luminous blue variables,

nearby low mass main sequence stars, cool subdwarf stars, and white

dwarfs. These observations will help us to (1) identify systems suitable

for follow up studies for mass determination, (2) study the role of

binaries in stellar birth and in advanced evolutionary states, (3)

explore the fundamental properties of stars near the main sequence-brown

dwarf boundary, (4) understand the role of binaries for X-ray bright

systems, (5) find binaries among ancient and nearby subdwarf stars, and

(6) help calibrate the white dwarf mass - radius relation.

WFPC2 11966

The Recent Star Formation History of SINGS Galaxies

The Spitzer Legacy project SINGS provided a unique view of the current

state of star formation and dust in a sample of galaxies of all Hubble

types. This multi-wavelength view allowed the team to create current

star formation diagnostics that are independent of the dust content and

increased our understanding of the dust in galaxies. Even so, using the

SINGS data alone we can only make rough estimates of the recent star

formation history of these galaxies. The lack of high resolution

observations (especially U-band and H-alpha) means that it is impossible

to estimate the ages of young clusters. In addition, the low resolution

of the Spitzer and ground-based observations means that what appear to

be individual Spitzer sources can actually be composed of many

individual clusters with varying ages. We need to know the ages, star

formation histories, and extinction of these individual clusters to

understand how these clusters form and age and thus influence the

evolution of the galaxy. In this proposal we address this missing area

of SINGS by obtaining high-resolution WFPC2 UBVI & H-alpha observations

to not only accurately locate and determine the ages of the young

stellar clusters in the actively star forming SINGS galaxies but to also

address a variety of other scientific issues. Over 500 HST orbits and

500 hours of Spitzter observing time have been dedicated to observations

of the SINGS sample. But the HST observations have not been systematic.

By adding a relatively small fraction of this time for these requested

observations, we will greatly enhance the legacy value of the SINGS

observations by creating a uniform high resolution multi-wavelength HST

archive that matches the quality of the lower resolution SINGS archive.

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:

18382-4 - NCS Restart and Cooldown

18370-2 - Adjust NCS CPL Setpoint = -5.0º deg C

COMPLETED OPS NOTES: (None)

                       SCHEDULED      SUCCESSFUL 

FGS GSacq               07                   07                       

FGS REacq               07                   07                     

OBAD with Maneuver 28                   28                  

SIGNIFICANT EVENTS:

Flash Report:

At 015/14:40:34 UTC, the NCC circulator was successfully restarted.