Branimir Sesar
University of Washington
 

"Mapping the Milky Way's Halo with SDSS RR Lyrae Stars"
 

I will present an analysis of halo substructure traced by RR Lyrae stars in the SDSS stripe 82 region. The main result is the highly inhomogeneous spatial distribution of halo stars at galactocentric distances 5–100 kpc. I will present strong direct evidence, based on both RR Lyrae stars and main sequence stars, that the halo stellar number density profile significantly steepens beyond ∼30 kpc from the Galactic center. By using a novel method that simultaneously combines observations of RR Lyrae and main-sequence stars, and using photometric metallicity estimates for main-sequence stars derived from deep co-added u-band data, we measure the metallicity of the Sagittarius dSph tidal stream (trailing arm) to be 0.3 dex higher ([Fe/H] = −1.2) than that of surrounding halo field stars.