The escape speed curve of the Galaxy obtained from Gaia DR2 implies a heavy Milky Way

Giacomo Monari; Benoit Famaey; Ismael Carrillo; Tilmann Piffl; Matthias Steinmetz; Rosemary F. G. Wyse; Friedrich Anders; Cristina Chiappini; Katja Janssen

doi:10.1051/0004-6361/201833748

paper

The escape speed curve of the Galaxy obtained from Gaia DR2 implies a heavy Milky Way

arXiv:1807.04565 · doi:10.1051/0004-6361/201833748

Abstract

We measure the escape speed curve of the Milky Way based on the analysis of the velocity distribution of $\sim 2850$ counter-rotating halo stars from the Gaia DR2. The distances were estimated through the StarHorse code, and only stars with distance errors smaller than 10 per cent were used in the study. The escape speed curve is measured at Galactocentric radii ranging from $\sim 5$ kpc to $\sim 10.5$ kpc. The local Galactic escape at the Sun's position is estimated to be $v_{e} (r_{⊙}) = 580 \pm 63 km s^{- 1}$ , and it rises towards the Galactic center. 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 $240 km s^{- 1}$ , a dark matter mass $M_{200} = 1.2 8_{- 0.50}^{+ 0.68} \times 1 0^{12} M_{⊙}$ and a high concentration $c_{200} = 11.0 9_{- 1.79}^{+ 2.94}$ . Assuming the mass-concentration relation of $Λ$ CDM, we get $M_{200} = 1.5 5_{- 0.51}^{+ 0.64} \times 1 0^{12} M_{⊙}$ , $c_{200} = 7.9 3_{- 0.27}^{+ 0.33}$ , for a local circular velocity of $228 km s^{- 1}$ .

arXiv comment5 pages, 4 figures, accepted for publication on A&A Letters, v2 (published version)

The escape speed curve of the Galaxy obtained from Gaia DR2 implies a heavy Milky Way

Abstract

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