Milky Way thin and thick disk kinematics with GAIA EDR3 and RAVE DR5

TL;DR

This study uses GAIA EDR3 and RAVE DR5 data to analyze the kinematics of Milky Way's thin and thick disks, revealing distinct velocity properties and the significant presence of thick disk stars up to 500 pc from the galactic plane.

Contribution

It provides a detailed kinematic analysis of RGB stars in the Milky Way's disk, identifying two distinct components and their properties using a large, complete stellar sample.

Findings

Identification of thin and thick disk kinematic properties.

Thick disk stars constitute about half the local stellar population up to 500 pc.

Supports secular evolution as the origin of the thick disk.

Abstract

We present a detailed analysis of kinematics of the Milky Way disk in solar neighborhood using GAIA DR3 catalog. To determine the local kinematics of the stellar disks of the Milky Way galaxy we use a complete sample of 278,228 red giant branch (RGB) stars distributed in a cylinder, centered at the Sun with a 1 kpc radius and half-height of 0.5 kpc. We determine separately the kinematical properties of RGB stars for each Galactic hemisphere in search for possible asymmetries. The kinematical properties of the RGB stars reveal the existence of two kinematically distinct components: the thin disk with mean velocities ${V_R}, {V_{\phi}}, {V_Z}$ of about -1, -239, 0 km s$^{-1}$ correspondingly and velocity dispersions $\sigma_R, \sigma_{\phi}, \sigma_Z$ of 31, 20 and 11 km s$^{-1}$, and the Thick disk with mean velocities components of about +1, -225, 0 km s$^{-1}$, and velocity dispersions of 49, 35, and 22 km s$^{-1}$. We find that up to 500 pc height above/below the galactic plane, Thick disk stars comprise about half the stars of the disk. Such high amount of RGB stars with Thick disk kinematics points at the secular evolution scenario origin for the Thick disk of the Milky Way galaxy.