HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT       # 4571

PERIOD COVERED: UT March 19, 2008 (DOY 079)

OBSERVATIONS SCHEDULED

WFPC2 10905

The Dynamic State of the Dwarf Galaxy Rich Canes Venatici I Region

With accurate distances, the nearest groups of galaxies can be resolved

in 3 dimensions and the radial component of the motions of galaxies due

to local density perturbations can be distinguished from cosmological

expansion components. Currently, with the ACS, galaxy distances within 8

Mpc can be measured effectively and efficiently by detecting the tip of

the red giant branch {TRGB}. Of four principal groups at high galactic

latitude in this domain, the Canes Venatici I Group {a} is the least

studied, {b} is the most populated, though overwhelmingly by dwarf

galaxies, and {c} is likely the least dynamically evolved. It is

speculated that galaxies in low mass groups may fail to retain baryons

as effectively as those in high mass groups, resulting in significantly

higher mass-to-light ratios. The CVn I Group is suspected to lie in the

mass regime where the speculated astrophysical processes that affect

baryon retention are becoming important.

FGS 11212

Filling the Period Gap for Massive Binaries

The current census of binaries among the massive O-type stars is

seriously incomplete for systems in the period range from years to

millennia because the radial velocity variations are too small and the

angular separations too close for easy detection. Here we propose to

discover binaries in this observational gap through a Faint Guidance

Sensor SNAP survey of relatively bright targets listed in the Galactic O

Star Catalog. Our primary goal is to determine the binary frequency

among those in the cluster/association, field, and runaway groups. The

results will help us assess the role of binaries in massive star

formation and in the processes that lead to the ejection of massive

stars from their natal clusters. The program will also lead to the

identification of new, close binaries that will be targets of long term

spectroscopic and high angular resolution observations to determine

their masses and distances. The results will also be important for the

interpretation of the spectra of suspected and newly identified binary

and multiple systems.

FGS 11295

Trigonometric Calibration of the Distance Scale for Classical Novae

The distance scale for classical novae is important for understanding

the stellar physics of their thermonuclear runaways, their contribution

to Galactic nucleosynthesis, and their use as extragalactic standard

candles. Although it is known that there is a relationship between their

absolute magnitudes at maximum light and their subsequent rates of

decline--the well-known maximum-magnitude rate-of-decline {MMRD}

relation--it is difficult to set the zero-point for the MMRD because of

the very uncertain distances of Galactic novae. We propose to measure

precise trigonometric parallaxes for the quiescent remnants of the four

nearest classical novae. We will use the Fine Guidance Sensors, which

are proven to be capable of measuring parallaxes with errors of ~0.2

mas, well below what is possible from the ground.

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration - CR Persistence Part 6

A new procedure proposed to alleviate the CR-persistence problem of

NICMOS. Dark frames will be obtained immediately upon exiting the SAA

contour 23, and every time a NICMOS exposure is scheduled within 50

minutes of coming out of the SAA. The darks will be obtained in parallel

in all three NICMOS Cameras. The POST-SAA darks will be non-standard

reference files available to users with a USEAFTER date/time mark. The

keyword 'USEAFTER=date/time' will also be added to the header of each

POST-SAA DARK frame. The keyword must be populated with the time, in

addition to the date, because HST crosses the SAA ~8 times per day so

each POST-SAA DARK will need to have the appropriate time specified, for

users to identify the ones they need. Both the raw and processed images

will be archived as POST-SAA DARKSs. Generally we expect that all NICMOS

science/calibration observations started within 50 minutes of leaving an

SAA will need such maps to remove the CR persistence from the science i

mages. Each observation will need its own CRMAP, as different SAA

passages leave different imprints on the NICMOS detectors.

NIC3 11107

Imaging of Local Lyman Break Galaxy Analogs: New Clues to Galaxy

Formation in the Early Universe

We have used the ultraviolet all-sky imaging survey currently being

conducted by the Galaxy Evolution Explorer {GALEX} to identify for the

first time a rare population of low-redshift starbursts with properties

remarkably similar to high-redshift Lyman Break Galaxies {LBGs}. These

"compact UV luminous galaxies" {UVLGs} resemble LBGs in terms of size,

SFR, surface brightness, mass, metallicity, kinematics, dust, and color.

The UVLG sample offers the unique opportunity of investigating some very

important properties of LBGs that have remained virtually inaccessible

at high redshift: their morphology and the mechanism that drives their

star formation. Therefore, in Cycle 15 we have imaged 7 UVLGs using ACS

in order to 1} characterize their morphology and look for signs of

interactions and mergers, and 2} probe their star formation histories

over a variety of timescales. The images show a striking trend of small-

scale mergers turning large amounts of gas into vigorous starbursts {a

process referred to as dissipational or "wet" merging}. Here, we propose

to complete our sample of 31 LBG analogs using the ACS/SBC F150LP {FUV}

and WFPC2 F606W {R} filters in order to create a statistical sample to

study the mechanism that triggers star formation in UVLGs and its

implications for the nature of LBGs. Specifically, we will 1} study the

trend between galaxy merging and SFR in UVLGs, 2} artificially redshift

the FUV images to z=1-4 and compare morphologies with those in similarly

sized samples of LBGs at the same rest-frame wavelengths in e.g. GOODS,

UDF, and COSMOS, 3} determine the presence and morphology of significant

stellar mass in "pre- burst" stars, and 4} study their immediate

environment. Together with our Spitzer {IRAC+MIPS}, GALEX, SDSS and

radio data, the HST observations will form a unique union of data that

may for the first time shed light on how the earliest major episodes of

star formation in high redshift galaxies came about. This proposal was

adapted from an ACS HRC+WFC proposal to meet the new Cycle 16 observing

constraints, and can be carried out using the ACS/SBC and WFPC2 without

compromising our original science goals.

NIC3 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

4.5<z<6.5, 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.

WFPC2 11198

Pure Parallel Imaging in the NDWFS Bootes Field

The NOAO Deep-Wide Field Survey {NDWFS} Bootes field is the target of

one of the most extensive multiwavelength campaigns in astronomy. In

addition to ground-based optical and near-infrared imaging, deep radio

mapping, and extensive spectroscopy, this entire region has been imaged

by the Chandra, Spitzer {IRAC and MIPS}, and GALEX missions. Robust

photometric redshifts {calibrated using over 20,000 spectroscopic

redshifts} exist for all sources brighter than R=24.5 or than 13 uJy at

4.5 microns. To enhance the value of this data set, we propose pure

parallel observations for all approved Cycle 16 programs in this region

that lack coordinated parallel observations. The primary aim of this

program will be to provide a database useful for the broad range of

science programs underway in this region.

WFPC2 11207

Star Formation in the Perseus Cluster Cooling Flow

We propose to obtain high resolution, UV/optical imaging of the

"accretion populations" in the massive cooling flow of the Perseus

cluster of galaxies. New GALEX observations show that the dominant

galaxy in this nearby cluster, NGC 1275, has an extended network of

UV-bright populations apparently formed recently from the intracluster

gas. Cluster cooling flows are the most prominent of the environments

where we can readily observe the cycle of gas accretion, star formation,

and feedback from active nuclei that is thought to play a central role

in the formation and evolution of galaxies. Because they can be readily

age-dated, the accretion populations help to trace the sequence of

exchange of material between galaxies and the intracluster medium. The

ACS/SBC and WFPC2/PC cameras offer the highest spatial resolution and

best panchromatic performance available to map the spatial and age

distribution of the accretion populations and their relationship to

radio-emitting plasma and the hot intracluster gas.

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                07                 07                

FGS REacq                07                 07                 

OBAD with Maneuver 28                  28                 

SIGNIFICANT EVENTS: (None)