Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stellar Velocity Dispersion and Anisotropy of the Milky Way Inner Halo   We measure the three components of velocity dispersion,
$\sigma_{R},\sigma_{\theta},\sigma_{\phi}$, for stars within 6 < R < 30 kpc of
the Milky Way using a new radial velocity sample from the MMT telescope. 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(<12 kpc) =
$1.3\times10^{11}$ M$_{\odot}$ with an uncertainty of 40%. We also find a
region of discontinuity, 15 < R < 25 kpc, where the estimated velocity
dispersions and anisotropies diverge from their anticipated values, confirming
at high significance the break observed by others. We argue that this break in
anisotropy is physically explained by coherent stellar velocity structure in
the halo, such as the Sgr stream. To significantly improve our understanding of
halo kinematics will require combining radial velocities with future Gaia
proper motions.

29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
15
The categories of this paper are: nucl-ex
3
The categories of this paper are: physics
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas