Kinematics of Stellar Populations with RAVE Data

Abstract

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.

27 pages, 7 figures, accepted for publication in New Astronomy

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Cited by in corpus (10)

• Chemical gradients in the Milky Way from the RAVE data. I. Dwarf stars
• Chemical gradients in the Milky Way from the RAVE data. II. Giant stars
• The relation between chemical abundances and kinematics of the Galactic disc with RAVE
• Local stellar kinematics from RAVE data: II. Radial Metallicity Gradient
• Thick disk kinematics from RAVE and the solar motion
• Thin disk kinematics from RAVE and the solar motion
• Local Stellar Kinematics from RAVE data - VII. Metallicity Gradients from Red Clump Stars
• The Galactic thin and thick disk
• Velocity-space substructure from nearby RAVE and SDSS stars
• Accurate Atmospheric Parameters at Moderate Resolution Using Spectral Indices: Preliminary Application to the MARVELS Survey