The Escape Velocity Profile of the Milky Way from Gaia DR3

Abstract

The escape velocity profile of the Milky Way offers a crucial and independent measurement of its underlying mass distribution and dark matter properties. Using a sample of stars from Gaia DR3 with 6D kinematics and strict quality cuts, we obtain an escape velocity profile of the Milky Way from 4 kpc to 11 kpc in Galactocentric radius. To infer the escape velocity in radial bins, we model the tail of the stellar speed distribution with both traditional power law models and a new functional form that we introduce. While power law models tend to rely on extrapolation to high speeds, we find our new functional form gives the most faithful representation of the observed distribution. Using this for the escape velocity profile, we constrain the properties of the Milky Way's dark matter halo modeled as a Navarro-Frenck-White profile. Combined with constraints from the circular velocity at the solar position, we obtain a concentration and mass of $c_{200\mathrm{c}}^{\mathrm{DM}}=13.9_{-4.3}^{+6.2}$ and ${\mathrm{M}}_{200\mathrm{c}}^{\mathrm{DM}}=0.55_{-0.14}^{+0.15}\times 10^{12}{\mathrm{M}}_{\odot }$. This corresponds to a total Milky Way mass of ${\mathrm{M}}_{200\mathrm{c}}=0.64_{-0.14}^{+0.15}\times 10^{12}{\mathrm{M}}_{\odot }$, which is on the low end of the historic range of the Galaxy's mass, but in line with other recent estimates.

26 pages, 13 figures, published in ApJ. Typo fixed in Eq. 7

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