2018A&A...616L...9M

We measure the escape speed curve of the Milky Way based on the analysis of the velocity distribution of ∼2850 counter-rotating halo stars from the Gaia Data Release 2. The distances were estimated through the StarHorse code, and only stars with distance errors smaller than 10% were used in the study. The escape speed curve is measured at Galactocentric radii ranging from ∼5kpc to ∼10.5kpc. The local Galactic escape at the Sun's position is estimated to be v_e(r_☉)=580±63km/s, and it rises towards the Galactic centre. Defined as the minimum speed required to reach three virial radii, our estimate of the escape speed as a function of radius implies for a Navarro-Frenk-White profile and local circular velocity of 240km/s a dark matter mass M₂₀₀=1.28_–0.50^+0.68x10¹²M_☉ and a high concentration c₂₀₀=11.09_–1.79^+2.94. Assuming the mass-concentration relation of ΛCDM, we obtain M₂₀₀=1.55_–0.51^+0.64x10¹²M_☉ and c₂₀₀=7.93_–0.27^+0.33 for a local circular velocity of 228km/s.