Correlations between age, kinematics, and chemistry as seen by the RAVE survey

TL;DR

This study investigates how stellar age, chemical composition, and movement patterns are interconnected in the Milky Way, revealing significant differences based on age and metallicity, and highlighting the influence of galactic structures.

Contribution

It provides new insights into the correlations between stellar properties and Galactic dynamics using a large RAVE survey dataset with age, chemistry, and kinematic analysis.

Findings

Metal-rich young stars show a steeper radial velocity gradient than metal-poor stars.

Young, metal-rich stars lag the local standard of rest with a positive gradient in azimuthal velocity.

Metal-poor stars exhibit a negative azimuthal velocity gradient above the LSR.

Abstract

We explore the connections between stellar age, chemistry, and kinematics across a Galactocentric distance of $7.5 < R\,(\mathrm{kpc}) < 9.0$, using a sample of $\sim 12\,000$ intermediate-mass (FGK) turnoff stars observed with the RAdial Velocity Experiment (RAVE) survey. The kinematics of this sample are determined using radial velocity measurements from RAVE, and parallax and proper motion measurements from the Tycho-Gaia Astrometric Solution (TGAS). In addition, ages for RAVE stars are determined using a Bayesian method, taking TGAS parallaxes as a prior. We divide our sample into young ($0 < \tau < 3$ Gyr) and old ($8 < \tau < 13$ Gyr) populations, and then consider different metallicity bins for each of these age groups. We find significant differences in kinematic trends of young and old, metal-poor and metal-rich, stellar populations. In particular, we find a strong metallicity dependence in the mean Galactocentric radial velocity as a function of radius ($\partial {V_{\rm R}}/\partial R$) for young stars, with metal-rich stars having a much steeper gradient than metal-poor stars. For $\partial {V_{\phi}}/\partial R$, young, metal-rich stars significantly lag the LSR with a slightly positive gradient, while metal-poor stars show a negative gradient above the LSR. We interpret these findings as correlations between metallicity and the relative contributions of the non-axisymmetries in the Galactic gravitational potential (the spiral arms and the bar) to perturb stellar orbits.