Volume 616, August 2018
|Number of page(s)||5|
|Section||Letters to the Editor|
|Published online||20 August 2018|
Letter to the Editor
The escape speed curve of the Galaxy obtained from Gaia DR2 implies a heavy Milky Way
Leibniz – Institut fuer Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
2 Université de Strasbourg, Observatoire astronomique de Strasbourg, CNRS UMR 7550, 11 rue de l’Université, 67000 Strasbourg, France
3 Department of Physics & Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
4 Leverhulme Trust Visiting Professor, University of Edinburgh, Edinburgh, UK
Accepted: 5 July 2018
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.
Key words: Galaxy: kinematics and dynamics / Galaxy: fundamental parameters
© ESO 2018
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