Mapping the Galactic Halo with SDSS, LINEAR and PTF RR Lyrae Stars
  We present an analysis of Galactic halo structure and substructure traced by
~500 RR Lyrae stars in the SDSS stripe 82 region. The main result of this study
is a 2D map of the Galactic halo that reaches distances of 100 kpc and traces
previously known and new halo substructures, such as the Sagittarius and Pisces
tidal streams. We also present strong direct evidence, based on both RR Lyrae
and main sequence stars, that the halo stellar number density profile
significantly steepens beyond 30 kpc from the Galactic center. Using a novel
photometric metallicity method that simultaneously combines data for RR Lyrae
and main sequence stars, we show that the median metallicity of the Sagittarius
trailing stream in the SDSS stripe 82 region is [Fe/H]}=-1.2 +- 0.1 dex. In
addition to these results, we will present ongoing work on a 3D map of the
Galactic halo constructed using a sample of ~4000 RR Lyrae stars that covers
8500 deg^2 of northern sky and probes up to 30 kpc from the Sun.
