Notice: Due to the conversion of some ACS WFC or HRC observations into

WFPC2, or NICMOS observations after the loss of ACS CCD science

capability in January, there may be an occasional discrepancy between a

proposal's listed (and correct) instrument usage and the abstract that

follows it.

HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT       # 4462

PERIOD COVERED: UT October 04, 2007 (DOY 277)

OBSERVATIONS SCHEDULED

ACS/SBC WFPC2 11175

UV Imaging to Determine the Location of Residual Star Formation in

Galaxies Recently Arrived on the Red Sequence

We have identified a sample of low-redshift {z = 0.04 - 0.10} galaxies

that are candidates for recent arrival on the red sequence. They have

red optical colors indicative of old stellar populations, but blue

UV-optical colors that could indicate the presence of a small quantity

of continuing or very recent star formation. However, their spectra lack

the emission lines that characterize star-forming galaxies. We propose

to use ACS/SBC to obtain high- resolution imaging of the UV flux in

these galaxies, in order to determine the spatial distribution of the

last episode of star formation. WFPC2 imaging will provide B, V, and I

photometry to measure the main stellar light distribution of the galaxy

for comparison with the UV imaging, as well as to measure color

gradients and the distribution of interstellar dust. This detailed

morphological information will allow us to investigate the hypothesis

that these galaxies have recently stopped forming stars and to compare

the observed distribution of the last star formation with predictions

for several different mechanisms that may quench star formation in

galaxies.

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 11080

Exploring the Scaling Laws of Star Formation

As a variety of surveys of the local and distant Universe are

approaching a full census of galaxy populations, our attention needs to

turn towards understanding and quantifying the physical mechanisms that

trigger and regulate the large-scale star formation rates {SFRs} in

galaxies.

WFPC2 11029

WFPC2 CYCLE 15 Intflat Linearity Check and Filter Rotation Anomaly

Monitor

Intflat observations will be taken to provide a linearity check: the

linearity test consists of a series of intflats in F555W, in each gain

and each shutter. A combination of intflats, visflats, and earthflats

will be used to check the repeatability of filter wheel motions.

{Intflat sequences tied to decons, visits 1-18 in prop 10363, have been

moved to the cycle 15 decon proposal xxxx for easier scheduling.} Note:

long-exposure WFPC2 intflats must be scheduled during ACS anneals to

prevent stray light from the WFPC2 lamps from contaminating long ACS

external exposures.

WFPC2 11079

Treasury Imaging of Star Forming Regions in the Local Group:

Complementing the GALEX and NOAO Surveys

We propose to use WFPC2 to image the most interesting star-forming

regions in the Local Group galaxies, to resolve their young stellar

populations. We will use a set of filters including F170W, which is

critical to detect and characterize the most massive stars, to whose hot

temperatures colors at longer wavelengths are not sensitive. WFPC2's

field of view ideally matches the typical size of the star-forming

regions, and its spatial resolution allows us to measure individual

stars, given the proximity of these galaxies. The resulting H-R diagrams

will enable studies of star-formation properties in these regions, which

cover largely differing metallicities {a factor of 17, compared to the

factor of 4 explored so far} and characteristics. The results will

further our understanding of the star-formation process, of the

interplay between massive stars and environment, the properties of dust,

and will provide the key to interpret integrated measurements of

star-formation indicators {UV, IR, Halpha} available for several

hundreds more distant galaxies. Our recent deep surveys of these

galaxies with GALEX {FUV, NUV} and ground-based imaging {UBVRI, Halpha,

[OIII] and [SII]} provided the identification of the most relevant SF

sites. In addition to our scientific analysis, we will provide catalogs

of HST photometry in 6 bands, matched corollary ground-based data, and

UV, Halpha and IR integrated measurements of the associations, for

comparison of integrated star-formation indices to the resolved

populations. We envisage an EPO component.

WFPC2 11103

A Snapshot Survey of The Most Massive Clusters of Galaxies

We propose the continuation of our highly successful SNAPshot survey of

a sample of 125 very X-ray luminous clusters in the redshift range

0.3-0.7. As demonstrated by the 25 snapshots obtained so far in Cycle14

and Cycle15 these systems frequently exhibit strong gravitational

lensing as well as spectacular examples of violent galaxy interactions.

The proposed observations will provide important constraints on the

cluster mass distributions, the physical nature of galaxy-galaxy and

galaxy-gas interactions in cluster cores, and a set of optically bright,

lensed galaxies for further 8-10m spectroscopy. All of our primary

science goals require only the detection and characterisation of

high-surface-brightness features and are thus achievable even at the

reduced sensitivity of WFPC2. Because of their high redshift and thus

compact angular scale our target clusters are less adversely affected by

the smaller field of view of WFPC2 than more nearby systems.

Acknowledging the broad community interest in this sample we waive our

data rights for these observations. Due to a clerical error at STScI our

approved Cycle15 SNAP program was barred from execution for 3 months and

only 6 observations have been performed to date - reinstating this SNAP

at Cycle16 priority is of paramount importance to reach meaningful

statistics.

WFPC2 11129

The Star Formation History of the Fornax Dwarf Spheroidal Galaxy

The Fornax dwarf spheroidal galaxy is one of the most luminous dwarf

satellites of the Milky Way. It is unusual in many ways: it hosts 5

globular clusters, shows some relatively young stars, and has faint

sub-structures which have been interpreted as signs of recent

interactions. It is thus of great interest to learn the complete star

formation history {SFH} of Fornax to establish a link between its

evolutionary path and the predictions from numerical simulations, as a

test of our understanding of dwarf galaxy evolution. Yet many questions

remain open. Is the old stellar population made up of stars formed in a

very early burst, perhaps before the epoch of reionisation, or the

result of a more continuous star formation between 13 and 9 Gyr ago ?

How quickly did Fornax increase its metallicity during its initial

assembly and during subsequent episodes of star formation ? Are

accretion episodes required to explain the age-metallicity history of

Fornax ? However, there has never been a comprehensive study of the

global SFH of the Fornax field based on data of sufficient depth to

unambiguously measure the age mixture of the stellar populations and

their spatial variation. We propose to use the WFPC2 to obtain very deep

images in several fields across the central region of Fornax in order to

reach the oldest main-sequence turnoffs. The number of fields is

determined by the need to measure the SFH over different regions with

distinct kinematics and metallicity. The resolution achievable with HST

is crucial to answer these questions because, to derive the age

distribution of the oldest stars, we are interested in I magnitude

differences of the order 0.2 mag in crowded fields at V=24.5. We will

directly measure the time variation in star-formation rate over the

entire galaxy history, from first stars coeval with the Milky Way halo

to the youngest populations 200 Myr ago. The combination of detailed CMD

analysis with WFPC2 with our existing metallicity and kinematic

information will allow us to trace out the early phases of its

evolution.

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                06                06                  

OBAD with Maneuver  26                26         

SIGNIFICANT EVENTS: (None)