The Mass and Extent of the Galactic Halo

We review the various techniques used to constrain the Galactic halo mass profile for radii > 20 kpc with particular emphasis on identifying a self-consistent halo model and resolving the apparent discrepancies present in the literature on this subject. We collate published results and demonstrate that they are all consistent with a Galactic halo that is nearly isothermal with a characteristic velocity of 180 to 220 km/sec and an extent >~ 200 kpc.