RAVE: Probing the galaxy's angular momentum through thick and thin (Disks and Halo)

The Radial Velocity Experiment (RAVE) is an ambitious all-sky spectroscopic survey to measure radial velocities and stellar atmosphere parameters (temperature, metallicity, surface gravity) of up to one million stars using the 6dF multi-object spectrograph on the 1.2-m UK Schmidt Telescope of the Anglo-Australian Observatory (AAO). We are analysing a subset of the first two years of RAVE data to quantify the distribution of the orbital angular momentum of RAVE stars to provide observational constraints for disk galaxy formation simulations. We use RAVE radial velocities of stars in the cardinal directions of Galactic longitude: l = 90 degrees (with Galactic rotation) and l = 270 degrees (against Galactic rotation). Radial velocities in these directions probe orbital angular momentum without requiring stellar distances. We plot Jz, the z (thin disk rotational symmetry axis) -component of the specific angular momentum of these stars, versus the specific binding energy of each star, E. The distribution of the "orbital circularity" parameter (Jz normalised by the specific angular momentum of that star if it was a circular orbit co-rotating with the thin disk) is plotted. Using reduced proper motion criteria, we statistically decompose the kinematics of our sample into local thin disk, local thick disk and local halo. We compare the relative distributions of the orbital circularity parameter for each of our kinematic components with those predicted by a simulated disk galaxy (Abadi et al. 2003, ApJ, 597,21)