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23 April 2024

» arxiv » 1309.4293

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The RAVE survey: the Galactic escape speed and the mass of the Milky Way
Til Piffl ; Cecilia Scannapieco ; James Binney ; Matthias Steinmetz ; Ralf-Dieter Scholz ; Mary E. K. Williams ; Roelof S. de Jong ; Georges Kordopatis ; Gal Matijevic ; Olivier Bienayme ; Joss Bland-Hawthorn ; Corrado Boeche ; Ken Freeman ; Brad Gibson ; Gerald Gilmore ; Eva K. Grebel ; Amina Helmi ; Ulisse Munari ; Julio F. Navarro ; Quentin Parker ; Warren A. Reid ; George Seabroke ; Fred Watson ; Rosemary F. G. Wyse ; Tomaz Zwitter ;
Date:	17 Sep 2013
Abstract:	We construct new estimates on the Galactic escape speed at various Galactocentric radii using the latest data release of the Radial Velocity Experiment (RAVE DR4). Compared to previous studies we have a database larger by a factor of 10 as well as reliable distance estimates for almost all stars. Our analysis is based on the statistical analysis of a rigorously selected sample of 90 high-velocity halo stars from RAVE and a previously published data set. We calibrate and extensively test our method using a suite of cosmological simulations of the formation of Milky Way-sized galaxies. Our best estimate of the local Galactic escape speed, which we define as the minimum speed required to reach three virial radii R340, is 537 +59 -43 km/s (90% confidence) with an additional 5% systematic uncertainty, where R340 is the Galactocentric radius encompassing a mean overdensity of 340 times the critical density for closure in the Universe. From the escape speed we further derive estimates of the mass of the Galaxy using a simple mass model with two options for the mass profile of the dark matter halo: an unaltered and an adiabatically contracted Navarro, Frenk & White (NFW) sphere. If we fix the local circular velocity the latter profile yields a significantly higher mass than the uncontracted halo, but if we instead use the statistics on halo concentration parameters in large cosmological simulations as a constraint we find very similar masses for both models. Our best estimate for M340, the mass interior to R340 (dark matter and baryons), is 1.4 +0.5 -0.3 x 10^12 M_sun (corresponding to M200 = 1.6 +0.5 -0.4 x 10^12 M_sun). This estimate is in good agreement with recently published independent mass estimates based on the kinematics of more distant halo stars and the satellite galaxy Leo I.
Source:	arXiv, 1309.4293
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