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 ≤ R ≤ 15.0 kpc and ∣Z∣ ≤ 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; for example, 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 these 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 disk flaring in the outer region (i.e., R ≥ 12 kpc), mostly for young or alpha-poor stellar populations. Our detailed measurements of age/[α/Fe]-velocity dispersion relations for different disk volumes indicate that young/α-poor populations are likely to originate from dynamic heating by both giant molecular clouds and spiral arms, while old/α-enhanced populations require an obvious contribution from other heating mechanisms, such as merger and accretion, or are born in the chaotic mergers of gas-rich systems and/or turbulent interstellar medium.