A lower bound on the Milky Way mass from general phase-space
  distribution function models
  We model the phase-space of the kinematic tracers using general, smooth
distribution functions to derive a conservative lower bound on the total mass
within 150-200 kpc.
  By approximating the potential as Keplerian, the phase-space distribution can
be simplified to that of a smooth distribution of energies and eccentricities.
Our approach naturally allows for calculating moments of the distribution
function, such as the radial profile of the orbital anisotropy. We construct a
family of phase-spaces with the resulting radial velocity dispersion
overlapping with that of distant kinematic tracers, while making no assumptions
about the density of the tracers and the radial profile of the velocity
anisotropy (beta).
  While there is no apparent upper bound for the Milky Way mass, at least as
long as only the radial motions are concerned, we find a sharp lower bound for
the mass that is small. In particular, a mass value of $2.4 \times 10^{11}$ of
solar masses, is still consistent with the dispersion profile at larger radii.
  Compared with much greater mass values in the literature, this result shows
that determining the Milky Way mass is strongly model dependent. We expect a
similar reduction of mass estimates in models assuming more realistic mass
profiles.
