NASA Hubble Space Telescope Daily Report # 4462
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 DAILY REPORT # 4462
– Continuing to collect World Class Science
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 images. 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)
