Radial velocities of Milky Way inner halo stars

We combine our measurements with previously published data so that we can more finely sample the stellar halo. We use a maximum likelihood statistical method for estimating mean velocities, dispersions, and covariances assuming only that velocities are normally distributed.

The alignment of the velocity ellipsoid is consistent with a spherically symmetric gravitational potential. From the spherical Jeans equation, the mass of the Milky Way is M(R<=12kpc)=1.3x10^11^M_{sun}_ with an uncertainty of 40%. We also find a region of discontinuity, 15<~R<~25kpc, where the estimated velocity dispersions and anisotropies diverge from their anticipated values, confirming the break observed by others.