AAS 207th Meeting, 8-12 January 2006
Session 131 Galactic Astronomy in the SDSS
Poster, Wednesday, 9:20am-6:30pm, January 11, 2006, Exhibit Hall

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[131.04] Estimation of Stellar Atmospheric Parameters from SDSS ugriz Photometry

Y. Lee, T. C. Beers (Michigan State & JINA), C. Bailer-Jones (MPIA), H. J. Newberg (RPI), M. Subbarao, D. Surendran (U. Chicago)

The SDSS survey, and its extension for Galactic studies, SEGUE, are obtaining broadband ugriz photometry for vast numbers of stars in the disk and halo populations of the Milky Way. There are two primary drivers for the development and refinement of techniques for estimation of approximate atmospheric parameters (Teff, log g, [Fe/H]) based on this photometry. First, the target selection algorithm for the roughly 250,000 stars that will be studied spectroscopically with SEGUE is based upon various cuts in ugriz parameter space, in hopes of optimally selecting stars of greatest interest for exploration of Galactic structure and kinematics, as well as for the indentification of low-metallicity stars. Secondly, if reasonably accurate estimates of the atmospheric parameters can be extracted from the photometry, this would allow for statistical studies of the nature of the metallicity distrution function throughout large regions of the Galaxy, and also aid in the identification of coherent streams of stellar debris that might share common abundances.

We report on investigations of several methods for the estimation of atmospheric parameters for stars with available SDSS photometry. These include the Principle Components Analysis technique originally explored by Lenz et al. (1998), as well as two new approaches based on supervised Artificial Neural Networks and Support Vector Machines. Focusing of the determination of [Fe/H], we compare estimated metallicities of field stars and members of several globular and open clusters based on SDSS R = 2000 spectroscopy with those obtained from the photometry alone. We comment on the suitability of these techniques over the wide range of temperature and surface gravity explored by SEGUE, and the impact of photometric errors on these estimates.

Y.L. and T.C.B. acknowledge partial support from grant AST 04-06784, as well as from grant PHY 02-16783, Physics Frontier Center/Joint Institute for Nuclear Astrophysics (JINA), awarded by the US National Science Foundation. H.J.N acknowledges partial support from NSF grant AST 03-07571.

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