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Estimation of the tilt of the stellar velocity ellipsoid from RAVE and implications for mass models.
MON NOT R ASTRON SOC
793 - 801.
We present a measure of the inclination of the velocity ellipsoid at 1 kpc below the Galactic plane using a sample of red clump giants from the RAdial Velocity Experiment (RAVE) Data Release 2. We find that the velocity ellipsoid is tilted towards the Galactic plane with an inclination of 7 degrees.3 +/- 1 degrees.8. We compare this value to computed inclinations for two mass models of the Milky Way. We find that our measurement is consistent with a short scalelength of the stellar disc (Rd similar or equal to 2 kpc) if the dark halo is oblate or with a long scalelength (Rd similar or equal to 3 kpc) if the dark halo is prolate. Once combined with independent constraints on the flattening of the halo, our measurement suggests that the scalelength is approximately halfway between these two extreme values, with a preferred range 2.5-2.7 kpc for a nearly spherical halo. Nevertheless, no model can be clearly ruled out. With the continuation of the RAVE survey, it will be possible to provide a strong constraint on the mass distribution of the Milky Way using refined measurements of the orientation of the velocity ellipsoid.
|Title:||Estimation of the tilt of the stellar velocity ellipsoid from RAVE and implications for mass models|
|Keywords:||stars: kinematics, galaxy: fundamental parameters, galaxy: kinematics and dynamics, SAGITTARIUS DWARF GALAXY, SKY SURVEY VIEW, DARK-MATTER HALO, MILKY-WAY, GALACTIC DISK, NEARBY STARS, SURFACE-DENSITY, TIDAL STREAMS, DATA RELEASE, HIPPARCOS|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Space and Climate Physics|
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