The Mass Profile of the Milky Way to the Virial Radius from the Illustris Simulation

Understand

We use particle data from the Illustris simulation, combined with individual kinematic constraints on the mass of the Milky Way (MW) at specific distances from the Galactic center, to infer the radial distribution of the MW's dark matter halo mass.

• Our method allows us to convert any constraint on the mass of the MW within a fixed distance to a full circular velocity profile to the MW's virial radius.
• As primary examples, we take two recent (and discrepant) measurements of the total mass within 50 kpc of the Galaxy and find they imply very different mass profiles and stellar masses for the Galaxy.
• The dark-matter-only version of the Illustris simulation enables us to compute the effects of galaxy formation on such constraints on a halo-by-halo basis; on small scales, galaxy formation enhances the density relative to dark-matter-only runs, while the total mass density is approximately 20% lower at large Galactocentric distances.