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Goals for the SDSS-II at JINA     

SEGUE: The Sloan Extension for Galactic Understanding and Exploration

SEGUE will provide fundamental data (imaging and medium-resolution spectroscopy) that will revolutionize our present understanding of the formation and evolution of the Milky Way galaxy. The most crucial information obtained with SEGUE will be spectroscopy of some 250,000 individual stars in the Milky Way, which will enable the identification and analysis of some 25,000 to 50,000 stars with metal abundances less than 1% of the solar value (a sample 50 times larger than available today). Such stars are of critical importance for understanding the production and evolution of the first elements in the Galaxy (and in the Universe). The data obtained by SEGUE will also enable studies of the structure of all known structural components of the Milky Way, including the stellar populations of the thin disk, the thick disk, and the inner and outer halo. The modern picture of the hierarchical assembly of the halo of the Milky Way from proto-dwarf galaxies will be strongly constrained by these data.

JINA Co-Investigator Timothy C. Beers (astronomer, Michigan State University, MSU) has coordinated the development of analysis techniques that employ SDSS photometry and spectroscopy to obtain estimates of the fundamental atmospheric properties of stars, e.g., their effective temperatures, surface gravities, and metal abundances. Based on these estimates, JINA scientists will select stars of greatest interest for constraining the evolution of the elements. These stars will, in turn, be studied at higher spectral resolution using facilities at the Hobby-Eberly 9.2m Telescope (HET) in Texas, with the Japanese National 8m Telescope (Subaru) in Hawaii, with the Large Binocular Telescope (LBT) in Arizona, with the Keck 10m telescope in Hawaii, and with the SOAR 4.1m telescope in Chile. Such high-resolution data will enable the identification of large samples of stars that exhibit over-abundances of neutron-capture elements, including the radioactive elements Thorium and Uranium, which are of fundamental importance for developing understanding of the same astrophysical processes that JINA is studying with laboratory facilities at Notre Dame and MSU, and by theoreticians seeking to understand the interactions of unstable nuclei involved with production of the elements in the early Universe.

SNS: Supernova Search with SDSS-II

Every fall during 2005-2007, the SDSS 2.5m telescope will continuously scan 200 square degrees of the sky near the south Galactic pole. This "movie of the sky" will reveal asteroids, comets, Galactic variable stars, extragalactic supernovae and bursts from active galactic nuclei. Supernovae are of special interest. The SDSS-II survey will find explosions in the "supernova desert": a distance range (0.1 < z < 0.3) that has seen very few supernova discoveries. But SDSS-II has the unique ability

to detect very faint events over a large search area and expects find about 200 type Ia supernovae in the desert.

The SDSS-II supernova survey will:

1) use the supernova light curves to measure the properties of dark energy that is accelerating the expansion of the universe.

2) study the diversity of supernovae and use that information to make them better distance indicators and more reliable cosmological probes.

3) match supernova characteristics with properties of their host galaxies including metallicity, star formation rate and star formation history. The large sample of SDSS-II events will provide clues to the progenitors of thermonuclear supernovae and impact of environment on the explosion energy.

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