Mapping the Galactic disk with the LAMOST and Gaia Red clump sample: VIII: Mapping the kinematics of the Galactic disk using mono-age and mono-abundance stellar populations

Abstract

We present a comprehensive study of the kinematic properties of the different Galactic disk populations, as defined by the chemical abundance ratios and stellar ages, across a large disk volume (4.5 $\le$ R $\le$ 15.0 kpc and $|Z|$ $\le$ 3.0 kpc), by using the LAMOST-Gaia red clump sample stars. We determine the median velocities for various spatial and population bins, finding large-scale bulk motions, such as the wave-like behavior in radial velocity, the north-south discrepancy in azimuthal velocity and the warp signal in vertical velocity, and the amplitudes and spatial-dependences of those bulk motions show significant variations for different mono-age and mono-abundance populations. The global spatial behaviors of the velocity dispersions clearly show a signal of spiral arms and, a signal of the disk perturbation event within 4 Gyr, as well as the disk flaring in the outer region (i.e., $R\ge 12$ kpc) mostly for young or alpha-poor stellar populations. Our detailed measurements of age/[$\hat{I}\pm$/Fe]-velocity dispersion relations for different disk volumes indicate that young/$\hat{I}\pm$-poor populations are likely originated from dynamically heated by both giant molecular clouds and spiral arms, while old/$\hat{I}\pm$-enhanced populations require an obvious contribution from other heating mechanisms such as merger and accretion, or born in the chaotic mergers of gas-rich systems and/or turbulent interstellar medium.

35 pages, 31 figures, 3 tables, accepted for publication in ApJ