TDF: Andrew Drake: Halo RR Lyrae from the Catalina Surveys

We have performed an extensive search for RR Lyrae among the 500 million sources observed by the Catalina Surveys. We detect ~26,000 type-AB RR Lyrae (of which 20,000 are new discoveries) from a region spanning 3/4 of the sky. By determining accurate distances to the stars, we investigate the spatial distribution of structures within the Milky Way halo. Combining the RR Lyrae distances with SDSS spectroscopy we are able accurately trace the velocities and metallicities of hundreds of sources within the Sagittarius tidal streams system. We find the first strong evidence for a dense tidal stream that overlaps the Sagittarius system to distances beyond 100kpc, yet remains unexplained by any existing model.