The Milky Way Tomography with SDSS: II. Stellar Metallicity
Abstract
Using effective temperature and metallicity derived from SDSS spectra for ~60,000 F and G type main sequence stars (0.2<g-r<0.6), we develop polynomial models for estimating these parameters from the SDSS u-g and g-r colors. We apply this method to SDSS photometric data for about 2 million F/G stars and measure the unbiased metallicity distribution for a complete volume-limited sample of stars at distances between 500 pc and 8 kpc. The metallicity distribution can be exquisitely modeled using two components with a spatially varying number ratio, that correspond to disk and halo. The two components also possess the kinematics expected for disk and halo stars. The metallicity of the halo component is spatially invariant, while the median disk metallicity smoothly decreases with distance from the Galactic plane from -0.6 at 500 pc to -0.8 beyond several kpc. The absence of a correlation between metallicity and kinematics for disk stars is in a conflict with the traditional decomposition in terms of thin and thick disks. We detect coherent substructures in the kinematics--metallicity space, such as the Monoceros stream, which rotates faster than the LSR, and has a median metallicity of [Fe/H]=-0.96, with an rms scatter of only ~0.15 dex. We extrapolate our results to the performance expected from the Large Synoptic Survey Telescope (LSST) and estimate that the LSST will obtain metallicity measurements accurate to 0.2 dex or better, with proper motion measurements accurate to ~0.2 mas/yr, for about 200 million F/G dwarf stars within a distance limit of ~100 kpc (g<23.5). [abridged]
Cite
@article{arxiv.0804.3850,
title = {The Milky Way Tomography with SDSS: II. Stellar Metallicity},
author = {Zeljko Ivezic and Branimir Sesar and Mario Juric and Nicholas Bond and Julianne Dalcanton and Constance M. Rockosi and Brian Yanny and Heidi J. Newberg and Timothy C. Beers and Carlos Allende Prieto and Ron Wilhelm and Young Sun Lee and Thirupathi Sivarani and John E. Norris and Coryn A. L. Bailer-Jones and Paola Re Fiorentin and David Schlegel and Alan Uomoto and Robert H. Lupton and Gillian R. Knapp and James E. Gunn and Kevin R. Covey and J. Allyn Smith and Gajus Miknaitis and Mamoru Doi and Masayuki Tanaka and Masataka Fukugita and Steve Kent and Douglas Finkbeiner and Jeffrey A. Munn and Jeffrey R. Pier and Tom Quinn and Suzanne Hawley and Scott Anderson and Furea Kiuchi and Alex Chen and James Bushong and Harkirat Sohi and Daryl Haggard and Amy Kimball and John Barentine and Howard Brewington and Mike Harvanek and Scott Kleinman and Jurek Krzesinski and Dan Long and Atsuko Nitta and Stephanie Snedden and Brian Lee and Hugh Harris and Jonathan Brinkmann and Donald P. Schneider and Donald G. York},
journal= {arXiv preprint arXiv:0804.3850},
year = {2008}
}
Comments
40 pages, 21 figures, emulateApJ style, accepted to ApJ, high resolution figures are available from http://www.astro.washington.edu/ivezic/sdss/mw/astroph0804.3850