The RAVE survey: constraining the local Galactic escape speed
Abstract
We report new constraints on the local escape speed of our Galaxy. Our analysis is based on a sample of highvelocity stars from the RAVE survey and two previously published data sets. We use cosmological simulations of disc galaxy formation to motivate our assumptions on the shape of the velocity distribution, allowing for a significantly more precise measurement of the escape velocity compared to previous studies. We find that the escape velocity lies within the range 498 < v_{esc} < 608kms^{1} (90 per cent confidence), with a median likelihood of 544kms^{1}. The fact that v^{2}_{esc} is significantly greater than 2v^{2}_{circ} (where v_{circ} = 220kms^{1} is the local circular velocity) implies that there must be a significant amount of mass exterior to the solar circle, that is, this convincingly demonstrates the presence of a dark halo in the Galaxy. We use our constraints on v_{esc} to determine the mass of the Milky Way halo for three halo profiles. For example, an adiabatically contracted NFW halo model results in a virial mass of 1.42^{+1.14}_{0.54} × 10^{12}M_{solar} and virial radius of (90 per cent confidence). For this model the circular velocity at the virial radius is 142^{+31}_{21}kms^{1}. Although our halo masses are model dependent, we find that they are in good agreement with each other.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 August 2007
 DOI:
 10.1111/j.13652966.2007.11964.x
 arXiv:
 arXiv:astroph/0611671
 Bibcode:
 2007MNRAS.379..755S
 Keywords:

 Galaxy: fundamental parameters;
 Galaxy: kinematics and dynamics;
 Astrophysics
 EPrint:
 19 pages, 9 figures, MNRAS (accepted). v2 incorporates minor cosmetic revisions which have no effect on the results or conclusions