The mass of the Milky Way from satellite dynamics
  We present and apply a method to infer the mass of the Milky Way (MW) by
comparing the dynamics of MW satellites to those of model satellites in the
EAGLE cosmological hydrodynamics simulations. A distribution function (DF) for
galactic satellites is constructed from EAGLE using specific angular momentum
and specific energy, which are scaled so as to be independent of host halo
mass. In this 2-dimensional space, the orbital properties of satellite galaxies
vary according to the host halo mass. The halo mass can be inferred by
calculating the likelihood that the observed satellite population is drawn from
this DF. Our method is robustly calibrated on mock EAGLE systems. We validate
it by applying it to the completely independent suite of 30 AURIGA
high-resolution simulations of MW-like galaxies: the method accurately recovers
their true mass and associated uncertainties. We then apply it to ten classical
satellites of the MW with 6D phase-space measurements, including updated proper
motions from the GAIA satellite. The mass of the MW is estimated to be
$M_{200}^{\textnormal{MW}}=1.17_{-0.15}^{+0.21}\times10^{12}M_{\odot}$ (68\%
confidence limits). We combine our total mass estimate with recent mass
estimates in the inner regions of the Galaxy to infer an inner dark matter (DM)
mass fraction $M^\textnormal{DM}(<20~\rm{kpc})/M^\textnormal{DM}_{200}=0.12$
which is typical of ${\sim}10^{12}M_{\odot}$ $\Lambda$CDM haloes in
hydrodynamical galaxy formation simulations. Assuming an NFW profile, this is
equivalent to a halo concentration of
$c_{200}^{\textnormal{MW}}=10.9^{+2.6}_{-2.0}$.
