Mapping the Remote Milky Way Halo using BHB stars at 70 < r < 130 kpc

Abstract

We increase the number of remote halo tracers by using blue horizontal branch (BHB) stars out to Galactocentric distances of 130 kpc. We use SDSS EDR photometry and the VLT to detect 16 BHB stars at Galactocentric distances 70 < r < 130, and to measure their radial velocities. We find the mass of the Milky Way is M =1.7^{+3.0}_{-0.6} x 10^{12} solar masses. When completed this survey will: (i) substantially reduce the errors in the total mass and extent of the Milky Way halo, (ii) map the velocity space in a hitherto unexplored region of the halo.