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Here we present a kinematic study of the Galactic halo out to a radius of$\sim$ 60 kpc, using 4664 blue horizontal branch (BHB) stars selected from theSDSS/SEGUE survey, to determine key dynamical properties. Using a maximumlikelihood analysis, we determine the velocity dispersion profiles in sphericalcoordinates ($\sigma_{r}$, $\sigma_{\theta}$, $\sigma_{\phi}$) and theanisotropy profile ($\beta$). The radial velocity dispersion profile($\sigma_{r}$) is measured out to a galactocentric radius of $r \sim 60$ kpc,but due to the lack of proper-motion information, $\sigma_{\theta}$,$\sigma_{\phi}$ and $\beta$ could only be derived directly out to $r \sim25$kpc. From a starting value of $\beta\approx 0.5$ in the inner parts($9<r/\kpc<12$), the profile falls sharply in the range $r \approx 13-18$ kpc,with a minimum value of $\beta=-1.2$ at $r=17$ kpc, rising sharply at largerradius. In the outer parts, in the range $25<r/\kpc<56$, we predict the profileto be roughly constant with a value of $\beta\approx 0.5$. The newly discoveredkinematic anomalies are shown not to arise from halo substructures. We alsostudied the anisotropy profile of simulated stellar halos formed purely byaccretion and found that they cannot reproduce the sharp dip seen in the data.From the Jeans equation, we compute the stellar rotation curve ($v_{\rm circ}$)of the Galaxy out to $r \sim 25$ kpc. The mass of the Galaxy within $r \lesssim25$ kpc is determined to be $2.1 \times 10^{11}$ $M_{\sun}$, and with a3-component fit to $v_{\rm circ}(r)$, we determine the virial mass of the MilkyWay dark matter halo to be $M_{\rm vir} = 0.9 ^{+0.4}_{-0.3} \times 10^{12}$$M_{\sun}$ ($R_{\rm vir} = 249^{+34}_{-31}$ kpc).

Kinematics of the stellar halo and the mass distribution of the Milky Way using BHB stars