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Daily 3877
HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT # 3877 PERIOD COVERED: UT June 08, 2005 (DOY 159) OBSERVATIONS SCHEDULED ACS/HRC 10137 Cluster Archeology: The Origin of Ultra-compact Dwarf Galaxies Ultra-compact dwarf {UCD} galaxies are a new type of galaxy we have discovered in the central regions of the Fornax and Virgo galaxy clusters. Our most recent observations in the Fornax Cluster show that UCDs outnumber normal galaxies in the centre of that cluster. Here we propose snapshot imaging of UCDs in the Fornax and Virgo clusters to test theories of how these fascinating objects formed. In particular we wish to image Virgo cluster UCDs for which we have ground-based Keck spectroscopy to test predictions that they formed more recently than the Fornax UCDs. ACS/HRC 10182 Towards a Comprehensive Understanding of Type Ia Supernovae: The Necessity of UV Observations Type Ia supernovae {SNe Ia} are very important to many diverse areas of astrophysics, from the chemical evolution of galaxies to observational cosmology which led to the discovery of dark energy and the accelerating Universe. However, the utility of SNe Ia as cosmological probes depends on the degree of our understanding of SN Ia physics, and various systematic effects such as cosmic chemical evolution. At present, the progenitors of SNe Ia and the exact explosion mechanisms are still poorly understood, as are evolutionary effects on SN Ia peak luminosities. Since early-time UV spectra and light curves of nearby SNe Ia can directly address these questions, we propose an approach consisting of two observational components: {1} Detailed studies of two very bright, young, nearby SNe Ia with HST UV spectroscopy at 13 epochs within the first 1.5 months after discovery; and {2} studies of correlations with luminosity for five somewhat more distant Hubble-flow SNe Ia, for which relative luminosities can be determined with precision, using 8 epochs of HST UV spectroscopy and/or broad-band imaging. The HST data, along with extensive ground-based optical to near-IR observations, will be analyzed with state-of-the-art models to probe SN Ia explosion physics and constrain the nature of the progenitors. The results will form the basis for the next phase of precision cosmology measurements using SNe Ia, allowing us to more fully capitalize on the substantial past {and future} investments of time made with HST in observations of high-redshift SNe Ia. ACS/HRC 10375 Stability of the ACS CCD: Flat fielding, Photometry, Geometry This program will verify that the low frequency flat fielding, the photometry, and the geometric distortion are stable in time and across the field of view of the CCD detectors. A moderately crowded stellar field, located ~6' West of the center of the cluster 47 Tuc, is observed every three months with the WFC and HRC using the full suite of broad and narrow band filters. The same field has been observed during SMOV to derive low frequency corrections to the ground flats and to create a master catalogue of positions and magnitudes from dithered observations of the cluster. In Cycles 11-12, this field was observed again using single pointings at various roll angles. The positions and magnitudes of objects are used to monitor local and large scale variations in the plate scale and the sensitivity of the detectors. The Cycle 13 program will continue to monitor these effects and will derive an independent measure of the detector CTE. ACS/HRC/WFC 10389 ACS CCDs daily monitor - Cycle 13 - Part 2 This program consists of a set of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. The files, biases and dark will be used to create reference files for science calibration. This program will be for the entire lifetime of ACS. ACS/SBC 10231 Tracing the Reionization History of Intergalactic Helium out to Redshift 3.8 We have found He II absorption in a quasar at redshift 3.82 via our Cycle 12 program of UV snapshots. This is the highest redshift yet at which He II absorption has been observed, and we propose to study helium ionization in the IGM along this new, long, unobscured sightline to high-redshift. The object has UV flux comparable to that of the rare handful of other z3 quasars known to be suitable for helium studies, and it is also in the Continuous Viewing Zone. The proposed spectrum will allow us to study the evolution and properties of the IGM and ionizing radiation from z=3.8 {the IGM environment near the quasar} all the way down to z=2.8. This redshift range may span the epoch of helium reionization, and even extends to high enough redshift to enable improved helium opacity measures using both He II Ly-alpha and Ly-beta. This program is now approved to use ACS prism. NIC1 10143 Ultracool companions to the nearest L dwarfs We propose to conduct the most sensitive survey to date for low mass companions to nearby L dwarfs. We will use NICMOS to image targets drawn from a volume- complete sample of 70 L dwarfs within 20 parsecs. The combination of infrared imaging and proximity will allow us to search for T dwarf companions at separations as small as 1.6 AU. This is crucial, since no ultracool binaries are currently known with separations exceeding 15 AU. Only 10 dwarfs in this sample have previous HST observations primarily at optical wavelengths. With the increased sensitivity of our survey, we will provide the most stringent test to date of brown dwarf models which envisage formation as ejected stellar embryos. In addition, our observations will be capable of detecting binaries with mass ratios as low as 0.3, and will therefore also test the apparent preference for equal-mass ultracool binaries. Finally, our observations offer the best prospect to date of detecting companions significantly cooler than the coolest t dwarf currently known. NIC1/NIC2/NIC3 8792 NICMOS Post-SAA calibration - CR Persistence Part 3 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. NIC2 10418 Morphologies and Color Gradients of Galaxies with the Oldest Stellar Populations at High Redshifts We have isolated a sample of 9 luminous {~2L*} galaxies with the very oldest stellar populations at their respective redshifts. The galaxies have been found in radio- source fields chosen to be at the key redshifts z~1.5 and z~2.5, which allow the cleanest separation of old stellar populations from highly reddened starbursts with colors derived from standard filter combinations. Ground-based observations in excellent seeing and with adaptive optics of 3 of these galaxies indicate that all 3 are dominated by well relaxed disks of old stars, suggesting that the first large stellar systems to form in the universe were disks in which star formation proceeded extremely rapidly and efficiently. In order to test this conjecture, we are requesting NICMOS2 exposures of our sample to obtain high S/N imaging in the F160W filter to determine detailed morphologies of the old stellar population, coupled with either NICMOS2 F110W or ACS F814W exposures {depending on redshift} to determine color gradients and/or other systematic color variations that might provide clues to formation processes. NIC2 10428 The colours of QSO host galaxies at z=2 and the evolution of their stellar masses We propose to use NICMOS imaging to measure the rest-frame optical/UV colours of a complete sample of 10 QSO host galaxies at redshifts between z=1.5 and z=2. From our cycle 11 HST observations {the GEMS project} we know that QSO host galaxies at redshifts of z~1 show blue colors despite having early-type morphologies. This is in excellent agreement with recent SDSS results on low-z AGN hosts, suggesting that QSO-type activity in galaxies correlates strongly with the presence of a young stellar population. Our proposed NICMOS observations will allow us to test the validity of this hypothesis out to z~2, by relating the observed QSO host colours to those of normal galaxies at similar redshifts taken from GOODS. We have already established within GEMS that the QSO hosts in our sample possess substantial UV luminosities, most likely originating from young stars. Knowing rest-frame colors, we can estimate stellar ages and stellar masses. For the first time will it be possible to determine the evolution of stellar masses in QSO host galaxies from z=2, the epoch of maximum QSO activity, to the present. Our results will shed light on the relation between nuclear activity and the star formation history of galaxies, and how these processes may jointly drive the cosmic evolution of QSOs and galaxies. 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: 1347-0 - ACS FSW CS 4.01 (JV0017P01) Load Delivery (F-string) @ 159/1936z SCHEDULED SUCCESSFUL FAILURE TIMES FGS Gsacq 7 7 FGS Reacq 8 8 FHST Update 14 14 LOSS of LOCK SIGNIFICANT EVENTS: (None) |
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