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 (DM) properties. Using a sample of stars from the third data release of Gaia with 6D kinematics and strict quality cuts, we obtain an escape velocity profile of the Milky Way from 4 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 DM 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 ${c}_{200c}^{\mathrm{DM}}={13.9}_{-4.3}^{+6.2}$ and ${M}_{200c}^{{\rm{DM}}}={0.55}_{-0.14}^{+0.15}\times {10}^{12}\,{M}_{\odot }$ . This corresponds to a total Milky Way mass of ${M}_{200c}={0.64}_{-0.14}^{+0.15}\times {10}^{12}\,{M}_{\odot }$ , which is on the low end of the historic range of the galaxy’s mass, but in line with other recent estimates.

Keywords

• Milky Way dynamics
• Stellar kinematics
• Galaxy stellar halos