The 3D Velocity Structure of the Thick Disk from SPM4 and RAVE DR2

Abstract

We analyze the 3D kinematics of a sample of $\sim 4400$ red clump stars ranging between 5 and 10 kpc from the Galactic center and up to 3 kpc from the Galactic plane. This sample is representative for the metal-rich ([Fe/H] = -0.6 to 0.5) thick disk. Absolute proper motions are from the fourth release of the Southern Proper Motion Program, and radial velocities from the second release of the Radial Velocity Experiment. The derived kinematical properties of the thick disk include: the rotational velocity gradient $\partial V_{\theta }/\partial z=-25.2\pm 2.1$ km s${}^{-1}$ kpc${}^{-1}$, velocity dispersions $({\sigma }_{V_R},{\sigma }_{V_{\theta }},{\sigma }_{V_z}){|}_{z=1}=(70.4,48.0,36.2)\pm (4.1,8.3,4.0)$ km s${}^{-1}$, and velocity-ellipsoid tilt angle $α_{Rz} = 8.6\arcdeg \pm 1.8 \arcdeg$. Our dynamical estimate of the thin-disk scale length is $R_{thin}=2.0\pm 0.4$ kpc and the thick-disk scale height is $z_{thick}=0.7\pm 0.1$ kpc. The observed orbital eccentricity distribution compared with those from four different models of the formation of the thick disk from Sales et al. favor the gas-rich merger model and the minor merger heating model. Interestingly, when referred to the currently accepted value of the LSR, stars more distant than 0.7 kpc from the Sun show a net average radial velocity of $13\pm 3$ km s${}^{-1}$. This result is seen in previous kinematical studiesusing other tracers at distances larger than $\sim 1$ kpc. We suggest this motion reflects an inward perturbation of the locally-defined LSR induced by the spiral density wave.

accepted for publication in ApJ

References in corpus (17)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• The Milky Way Tomography with SDSS: II. Stellar Metallicity
• Riding the Spiral Waves: Implications of Stellar Migration for the Properties of Galactic Disks
• Thin, thick and dark discs in LCDM
• The Radial Velocity Experiment (RAVE): second data release
• Light and Motion in SDSS Stripe 82: The Catalogues
• Cold Dark Matter Substructure and Galactic Disks II: Dynamical Effects of Hierarchical Satellite Accretion
• Kinematics at the Edge of the Galactic Bulge: Evidence for Cylindrical Rotation
• The Bulge Radial Velocity Assay (BRAVA): I. Sample Selection and a Rotation Curve
• Estimation of the Tilt of the Stellar Velocity Ellipsoid from RAVE and Implications for Mass Models
• Galactic kinematics with RAVE data: I. The distribution of stars towards the Galactic poles
• Velocity Shear of the Thick Disk from SPM3 Proper Motions at the South Galactic Pole
• Observational Evidence from SDSS for a Merger Origin of the Milky Way's Thick Disk
• Estimation of Galactic model parameters in high latitudes with 2MASS
• High resolution spectroscopic study of red clump stars in the Galaxy: iron group elements
• Mapping the Asymmetric Thick Disk: The Hercules Thick Disk Cloud
• Disentangling the Galaxy at low Galactic latitudes

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