The escape speed curve of the Galaxy obtained from Gaia DR2 implies a heavy Milky Way
Abstract
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 5 kpc to 10.5 kpc. The local Galactic escape at the Sun's position is estimated to be ve(r⊙) = 580 ± 63 km s-1, 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 240 km s-1 a dark matter mass M200 = 1.28-0.50+0.68 × 1012 M⊙ 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+0.64 × 1012 M⊙ and c200 = 7.93-0.27+0.33 for a local circular velocity of 228 km s-1.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- August 2018
- DOI:
- 10.1051/0004-6361/201833748
- arXiv:
- arXiv:1807.04565
- Bibcode:
- 2018A&A...616L...9M
- Keywords:
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- Galaxy: kinematics and dynamics;
- Galaxy: fundamental parameters;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 5 pages, 4 figures, accepted for publication on A&