Kinematics of Stellar Populations with RAVE Data
  We study the kinematics of the Galactic thin and thick disk populations using
stars from the RAVE survey's second data release together with distance
estimates from Breddels et al. (2009). The velocity distribution exhibits the
expected moving groups present in the solar neighborhood. We separate thick and
thin disk stars by applying the X (stellar-population) criterion of Schuster et
al. (1993), which takes into account both kinematic and metallicity
information. For 1906 thin disk and 110 thick disk stars classified in this
way, we find a vertical velocity dispersion, mean rotational velocity and mean
orbital eccentricity of (sigma_W, Vphi, e)_thin = (18\pm0.3 km/s, 223\pm0.4
km/s, 0.07\pm0.07) and (sigma_W, Vphi, e)_thick = (35\pm2 km/s, 163\pm2 km/s,
0.31\pm0.16), respectively. From the radial Jeans equation, we derive a thick
disk scale length in the range 1.5-2.2 kpc, whose greatest uncertainty lies in
the adopted form of the underlying potential. The shape of the orbital
eccentricity distribution indicates that the thick disk stars in our sample
most likely formed in situ with minor gas-rich mergers and/or radial migration
being the most likely cause for their orbits. We further obtain mean metal
abundances of <[M/H]>_thin = +0.03 \pm 0.17, and <[M/H]>_thick = -0.51\pm0.23,
in good agreement with previous estimates. We estimate a radial metallicity
gradient in the thin disk of -0.07 dex/kpc, which is larger than predicted by
chemical evolution models where the disk grows insideout from infalling gas. It
is, however, consistent with models where significant migration of stars shapes
the chemical signature of the disk, implying that radial migration might play
at least part of a role in the thick disk's formation.
