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DAILY REPORT #3902
HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science
DAILY REPORT #3902 PERIOD COVERED: UT July 14, 2005 (DOY 195) OBSERVATIONS SCHEDULED ACS/HRC 10094 Mid-Ultraviolet Spectral Templates for Old Stellar Systems We propose a three-year program to provide both observational and theoretical mid- ultraviolet {2300A -- 3100A} spectral templates for interpreting the age and metallicity of globular clusters and elliptical galaxies from spectra of their integrated light. The mid-UV is the region most directly influenced by stellar age, and is observed directly in optical and infrared studies of high-redshift quiescent systems. The reliability of age and metallicity determinations remains questionable until non-solar metallicities and abundance ratios are considered, and stars spanning the color-magnitude diagram are included, as we propose here. With archival HST STIS spectra we have improved the list of mid-UV atomic line parameters, then calculated spectra from first principles which match observed spectra of standard stars up to one- fourth solar metallicity. We will extend both observations and calculations to stars of solar metallicity and beyond, and to those in short-lived stages hotter than the main-sequence turnoff, stars not currently well-represented in empirical libraries. The necessary line-list improvements will come from new high-resolution mid-UV spectra of nine field stars. A key application of the results of this program will be to the old systems now being discovered as `Extremely Red Objects' at high redshifts. Reliable age-dating of these places constraints on the epoch when large structures first formed in the universe. ACS/HRC 10435 Merger-Induced Populations in Early-Type Galaxy Cores Hierarchical formation models predict that early-type galaxies are built up over an extended period from mergers of smaller systems, a process which should leave long- lived signatures in their light profiles and stellar population colors. Merger events should have continued up to relatively recent times {the last 1-5 Gyr}, and many ellipticals and S0 bulges should therefore show evidence of multiple, discrete, intermediate-age populations. Although there is substantial observational support for a dissipational merger origin for some early-type galaxies, most do not exhibit the expected anomalies in either their light profiles or color distributions. However, existing searches {mainly in the V and I bands} have not probed very deeply. Here we propose high resolution, broad-band, near-ultraviolet {2500-3400 A} imaging of the cores of bright early-type galaxies. This is the most sensitive probe available for the detection of spatially-segregated, multiple population components with ages in the range 1-5 Gyr. Our sample consists of dust- and AGN-free systems with both normal and mildly anomalous central light profiles. There is very little existing information on the near-UV structure of early-type galaxies, and our program would effectively explore new terrain. ACS/HRC 10627 A Snapshot Survey of Post-AGB Objects and Proto-Planetary Nebulae We propose an ACS/HRC snapshot survey of 50 post-AGB sources, objects which have evolved from the AGB but may or may not become planetary nebulae {PNe}. This survey will complement existing HST images of proto-planetary nebulae {PPNe} and PNe in addressing circumstellar envelope morphology as a function of: 1} the progenitor star mass; 2} the chemical composition; and 3} evolutionary stage. We will connect the observed diversity of nebualar shapes with the main physical and chemical conditions characterizing post-AGB objects, to identify the mechanism that breaks the symmetry of AGB mass loss. To our knowledge, no previous HST projects have been specifically designed to address this issue. From our database of 360 post-AGB candidates, we have selected approximately 50 targets, none of which have been or are being observed with HST, to sample different central star masses, chemical compositions, and evolutionary stages, uniformly across the sky. These new data will also provide important constraints to a quantitative analysis of Spitzer Space Telescope {SST} observations planned for a similar sample of objects. We will model the HST images and SST spectra using our axisymmetric dust code 2-Dust, to derive dust density distributions, pole to equator density ratios, dust shell masses, inclination angles as well as dust composition. ACS/HRC 9973 Intensive Coverage of the Eta Carinae Event in 2003 For a variety of reasons, HST can provide a very special and unique data set when Eta Car experiences its next spectroscopic event in mid-2003. Explaining the phenomenon is only part of the motivation. This star and its ejecta have unique characteristics that make them important for several branches of astrophysics; and when a spectroscopic event occurs, it's like varying the parameters in an experiment {or rather, set of experiments}. The 2003 event may be the only chance in the forseeable future to obtain such a data set, especially with HST. Eta Carinae has extreme parameters; it is mysterious in surprisingly basic ways; and HST/ACS/HRC can gather useful data on it at a terrific rate. As we explain below, the proposed data set will be valuable in several independent ways: It will help solve a specific set of current problems, it will constitute a large and unique archival data base for both stellar and nebular astrophysics, and it will be well-suited for educational uses. ACS/WFC 10235 Dark vs. luminous matter in the CenA/M83 galaxy complex The distribution of dark vs. luminous matter on scales of 0.1-1.0 Mpc remains poorly understood. For a nearby group, the total mass can be determined from the radius of "the zero-velocity surface", which separates the group from the general Hubble flow. This new method requires the measurement of accurate distances and radial velocities of galaxies around the group, but gives total mass estimates independent of assumptions about the state of relaxation or orbital characteristics. The mass pertains to the group at the full scale to which it is bound. Upon application in several nearest groups, the method yields mass estimates in agreement with the sum of the virial masses of subcomponents. However, the typical total M/L ratio for the nearby groups of ~30 Mo/Lo implies a local mean density of matter which is only 1/7 the canonical global density . The nearby complex of galaxies around Cen A and M83 resembles our Local Group by the dumb-bell concentration of objects around a pair of dominant galaxies. Accurate distances have been acquired recently for ~20 group members by the TRGB method using HST. We will measure TRGB distances to the 17 remaining galaxies in the region. These observations will constrain the dynamical state of the halo surrounding the nearest giant E-galaxy Cen A, providing a comparison with the halos of the nearest spirals. ACS/WFC 10412 The host galaxies of dust-reddened quasars We have used the 2MASS near-infrared and FIRST radio surveys, together with the Palomar Observatory Sky Survey plates to select a sample of dust-reddened, radio- intermediate quasars. We wish to use ACS to study the host galaxies of these quasars. The dust reddening of the quasars makes it possible to study the hosts at rest-frame optical-UV wavelengths much more easily than the hosts of normal quasars of similar bolometric luminosity. Our study will compare the hosts of our dust-reddened quasars to those of normal quasars from the HST archive to test the hypothesis that dust-reddened quasars are young objects, whose hosts still show morphological evidence of recent merger events which triggered the quasar. 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: #17471-1: TMDIAG & PN Format for AOA @195/2000z #17473-0: GenSlew for Proposal 10425 Slot 10 @195/1902z #17474-0: GenSlew for Proposal 10425 Slot 09 @195/1904z COMPLETED OPS NOTES: (None) SCHEDULED SUCCESSFUL FGS Gsacq 6 6 FGS Reacq 9 9 FHST Update 9 9 SIGNIFICANT EVENTS: (None) |
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