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Daily #4027
HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT #4027 PERIOD COVERED: UT January 012, 2006 (DOY 012) OBSERVATIONS SCHEDULED ACS/SBC 10259 Planetary nebulae in the SMC: a study of stellar evolution and populations in an extremely low- metallicity environment The final phase of the evolution of low- and intermediate-mass stars, the planetary nebula {PN} ejection, is thought to largely contribute to the carbon and nitrogen enrichment in galaxies, in particular in old stellar populations. Stellar generations forming from a carbon- and nitrogen- enriched medium are a necessary condition for planetary and life formation. It is essential to understand how stars go through the process of shedding their chemically-enriched shells, and to test the predictions of stellar evolution theory on the relationship between stellar mass and elemental enrichment. Magellanic Cloud PNs are ideal probes for this study. Their abundances can be directly related to the mass of the central stars and to that of the stellar progenitor, without the great {distance and reddening} uncertainties that affect Galactic PNs. The UV lines are essential for calculating the abundances of the element related to stellar evolution {C, N, O} and to progenitor populations {e.g., Ne}. We propose to acquire STIS UV spectroscopy of the SMC PNs whose morphology and central star properties has been previously determined by us with HST. We will derive the {C, N, O} abundance-to-mass relation, and determine the extent to which the mass of the progenitors of asymmetric PNs exceed that of symmetric PNs. We will also test the PN luminosity function, and probe cosmic recycling, in a very low-metallicity environment. ACS/WFC 10524 Blue Stragglers: a key stellar population to probe internal cluster dynamics This proposal is part of a coordinated project devoted to understand the interplay of globular cluster {GC} dynamics and the formation and evolution of blue straggler stars {BSS}. By using a combination of HST and ground-based observations we are constructing complete BSS surveys in a sample of GCs; complete BSS surveys require mid-UV HST observations in the center and wide field CCD ground based observations under excellent seeing conditions of the exterior. Up to now only four clusters have been surveyed in this way and the results are surprising: in three GCs {M3, 47 Tuc, NGC 6752} we have discovered that the BSS radial distribution is bimodal, highly peaked in the cluster center, rapidly decreasing at intermediate radii and rising again at large radii {Ferraro et al. 1997, 2004, Sabbi et al. 2004}, conversely BSS population in Omega Centauri does not show any signature of the segregation which would be expected for a class of objects arising from either stellar interactions or binarity {Ferraro et al. 2005}. These observational facts are opening a new prospective in the study of the formation processes and evolution of BSS in GCs. By using extensive simulations, we demonstrated that the spatial distribution of BSS observed in 47 Tuc can be only reproduced if a sizable fraction of BSS is generated {via mass transfer in primordial binaries} in the peripheral region of the cluster {Mapelli et al 2004}, thus excluding a purely collisional formation scenario. Here we propose mid-UV imaging of a few clusters suspected of harboring a large population of central BSS and a few known to have many BSS the external region. These are good candidates for determining accurate BSS radial distributions. The modest amount of time proposed here will go far to determine the ubiquity of BSS bimodality and to constrain models of dynamical evolution. Since we believe the proposed observations would be useful to the entire stellar community {for multifold purposes} we waive the propretary period. ACS/WFC 10543 Microlensing in M87 and the Virgo Cluster Resolving the nature of dark matter is an urgent problem. The results of the MACHO survey of the Milky Way dark halo toward the LMC indicate that a significant fraction of the halo consists of stellar mass objects. The VATT/Columbia survey of M31 finds a similar lens fraction in the M31 dark halo. We propose a series of observations with ACS that will provide the most thorough search for microlensing toward M87, the central elliptical galaxy of the Virgo cluster. This program is optimized for lenses in the mass range from 0.01 to 1.0 solar masses. By comparing with archival data, we can detect lenses as massive as 100 solar masses, such as the remnants of the first stars. These observations will have at least 15 times more sensitivity to microlensing than any previous survey, e.g. using WFPC2. This is due to the factor of 2 larger area, factor of more than 4 more sensitivity in the I-band, superior pixel scale and longer baseline of observations. Based on the halo microlensing results in the Milky Way and M31, we might expect that galaxy collisions and stripping would populate the overall cluster halo with a large number of stellar mass objects. This program would determine definitively if such objects compose the cluster dark matter at the level seen in the Milky Way. A negative result would indicate that such objects do not populate the intracluster medium, and may indicate that galaxy harassment is not as vigorous as expected. We can measure the level of events due to the M87 halo: this would be the best exploration to date of such a lens population in an elliptical galaxy. Star-star lensing should also be detectable. About 20 erupting classical novae will be seen, allowing to determine the definitive nova rate for this giant elliptical galaxy. We will determine if our recent HST detection of an M87 globular cluster nova was a fluke, or indicative of a 100x higher rate of incidence of cataclysmic variables and nova eruptions in globulars than previously believed. We will examine the populations of variable stars, and will be able to cleanly separate them from microlensing. ACS/WFC 10595 A Reference Database for Accurate Ages and Metallicities of Globular Clusters in the Magellanic Clouds We propose to finalize the compilation of a comprehensive database of high-quality ages and metallicities of Simple Stellar Populations {SSPs} in the Milky Way and the Magellanic Clouds. We will acquire new ACS imagery for 8 young and intermediate-age globular clusters in the Magellanic Clouds to create high-quality color-magnitude diagrams {CMDs} to enable accurate measurements of their ages and metallicities. In concert with a similar analysis of CMD data already available in the HST archive for 8 more such GCs, the resulting database will provide a well-sampled coverage of the full range of ages and metallicities known among globular clusters {0.5 = Age {Gyr} = 13.5 and -2.3 = [Fe/H] = +0.1, respectively}. This database will form the crucial basis for our ongoing, comprehensive multi-wavelength program to: {1} establish empirical relations among SSP colors {from the UV [GALEX] through the mid-IR [Spitzer]}, line strengths, ages and metallicities, and {2} provide a stringent test of the systemic accuracy of age and metallicity determinations using state-of-the-art population synthesis models. ACS/WFC/WFPC2 10499 Life Before the Fall: Morphological Evolution of Galaxies in Groups Prior to Cluster Assembly at z=0.37 We propose to obtain a deep ACS/WFC mosaic of a protocluster comprised of 4 distinct galaxy groups that are gravitationally bound to each other at z=0.37. The galaxy groups have a total combined mass comparable to the Coma cluster and already have twice as many absorption line galaxies as the field. The SG1120 complex thus provides an unprecedented opportunity for determining whether "pre-processing" in the group environment is responsible for the bulk of observed diffences between galaxies in nearby clusters and those in the field. High resolution imaging with HST is needed to morphologically classify the group members and measure their structural parameters. By combining the early-type fraction and morphology-density relation in SG1120 with results from our wide-field spectroscopic survey, we will test whether spectral and morphological transformation timescales are decoupled on group scales and isolate the environmental mechanisms responsible for such evolution. We will also measure the Fundamental Plane and M/L ratios of the early-type members to constrain their formation epoch and how their stellar populations have evolved. Observations of the multiple galaxy groups in SG1120 provide a unique dataset to the community and will aid our understanding of how galaxies evolve in the still poorly studied group regime. FGS 10613 Calibrating the Mass-Luminosity Relation at the End of the Main Sequence We propose to use HST-FGS1R to calibrate the mass-luminosity relation {MLR} for stars less massive than 0.2 Msun, with special emphasis on objects near the stellar/brown dwarf border. Our goals are to determine M_V values to 0.05 magnitude, masses to 5 than double the number of objects with masses determined to be less than 0.20 Msun. This program uses the combination of HST-FGS3/FGS1R at optical wavelengths and ground-based infrared interferometry to examine nearby, subarcsecond binary systems. The high precision measurements with HST-FGS3/FGS1R {to 1 mas in the separations} for these faint targets {V = 10--15} simply cannot be equaled by any ground based technique. As a result of these measurements, we are deriving high quality luminosities and masses for the components in the observed systems, and characterizing their spectral energy distributions from 0.5 to 2.2 Mum. Several of the objects included have M 0.1 Msun, placing them at the very end of the stellar main sequence. Three of the targets are brown dwarf candidates, including the current low mass record holder, GJ 1245C, with a mass of 0.062 +/- 0.004 Msun. The payoff of this proposal is high because all 10 of the systems selected have already been resolved with HST- FGS3/FGS1R during Cycles 5--10 and contain most of the reddest objects for which masses can be determined. NIC1/NIC2/NIC3 8793 NICMOS Post-SAA calibration - CR Persistence Part 4 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 10173 Infrared Snapshots of 3CR Radio Galaxies Radio galaxies are an important class of extragalactic objects: they are one of the most energetic astrophysical phenomena and they provide an exceptional probe of the evolving Universe, lying typically in high density regions but well-represented across a wide redshift range. In earlier Cycles we carried out extensive HST observations of the 3CR sources in order to acquire a complete and quantitative inventory of the structure, contents and evolution of these important objects. Amongst the results, we discovered new optical jets, dust lanes, face-on disks with optical jets, and revealed point-like nuclei whose properties support FR-I/BL Lac unified schemes. Here, we propose to obtain NICMOS infrared images of 3CR sources with z0.3 as a major enhancement to an already superb dataset. We aim to deshroud dusty galaxies, study the underlying host galaxy free from the distorting effects of dust, locate hidden regions of star formation and establish the physical characteristics of the dust itself. We will measure frequency and spectral energy distributions of point-like nuclei, expected to be stronger and more prevalent in the IR, seek spectral turnovers in known synchrotron jets and find new jets. We will strongly test unified AGN schemes and merge these data with existing X-ray to radio observations. The resulting database will be an incredibly valuable resource to the astronomical community for years to come. NIC3/ACS/WFC 10529 A Deep H-band Probe of the Globular Cluster Mass function We propose to obtain deep NICMOS H-band data for the globular clusters in the inner region of M87 and coordinated parallel ACS WFC g and z band observations of a second field which has very deep archival NICMOS data. Therefore, our proposed deep NICMOS observation overlaps corresponding deep archival optical data in the inner regions, and the parallel ACS observations overlap deep NICMOS images in the outer field. The combination of the sensitivity of the near infrared to the mass of old stellar systems such as the globular clusters in M87 and the ability of the optical to isolate the metal-rich and metal-poor subcomponents of the globular cluster system will allow us to probe the mass function, and the possible variation with metallicity, to unprecedented depths. These observations are critical to linking the commonly observed cluster luminosity function to the usually derived mass function in theoretical calculations of globular cluster and globular cluster system formation and evolution models. The multiple pointings will allow us to probe the radial variations in globular cluster properties and test the predictions of cluster formation and dynamical destruction models. Because of its extremely rich globular cluster system {~15, 000 clusters} M87 is one of the only galaxies in which such a study can be conducted with a statistically significant number of candidate clusters {approximately 300 globular clusters in this study} with efficient use of HST time. FLIGHT OPERATIONS SUMMARY: Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.) HSTARS: 10078 - REACQ(1,2,2) failed due to search radius limit exceeded on FGS 1 @ 012/10:04:27z REACQ(1,2,2) at 012/09:59:46 failed due to Search Radius Limit Exceeded on FGS 1 at 10:04:27. Primary GSACQ(1,2,2) at 08:35:09 was successful. OBAD after REACQ at 10:06:59 showed attitude error of 279.04 arc seconds on V2. COMPLETED OPS REQUEST: 17619-1 - Software Taper Charge Control @ 012/1156z 17625-0 - Modify SOC Benchmark & ACR 2 HI Limit @ 013/0010z COMPLETED OPS NOTES: (None) SCHEDULED SUCCESSFUL FAILURE TIMES FGS GSacq 07 07 FGS REacq 09 08 012/10:04:27z (HSTAR # 10078) OBAD with Maneuver 30 30 SIGNIFICANT EVENTS: Taper Charge Transition Flash Report - (12 Jan 2006 08:54:20, SE dlewis) - On DOY 2006/012 at approximately 13:27 Software Taper Charge Control was activated via Ops Request 17619. During the first orbit cycle after the transition, the system performed as expected - ACR set and reset the benchmark, recharge ratios, and the trickle charge elapse timer; SPA trim relays opened and closed via OCA. Moreover, the battery temperatures are slightly cooler, and the system SOC delta remained within 4 AH of the pre-test value. EPS SEs will continue to monitor the system and subsequent flash reports are forthcoming. Flash Report: FSW SOC Changes post-Taper Charge Transition Ops Briefing - (12 Jan 2006 18:30:53) - Summary Extract Follows -- Discussion/Agreements: The recommendation to reduce the benchmark to 234 Ah so that the end-of-orbit night FSW SOC is ~5 Ah above the end-of-orbit night pressure-based SOC was approved along with changing the ACR high limit to 3 batteries reaching cut-off. |
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