A Test for Radial Mixing Using Local Star Samples

TL;DR

This study uses local star samples to investigate how the radial metallicity gradient in the Milky Way's thin disk varies with stellar age, providing evidence for radial mixing driven by spiral patterns.

Contribution

It introduces a method to analyze the radial metallicity gradient as a function of stellar age using angular momentum and effective temperature proxies.

Findings

Radial metallicity gradient decreases with stellar age.

Evidence supports radial mixing caused by transient spiral arms.

Gradient trend flattens for stars older than the thin disk's age.

Abstract

We use samples of local main-sequence stars to show that the radial gradient of [Fe/H] in the thin disk of the Milky Way decreases with mean effective stellar temperature. Many of these stars are visiting the solar neighborhood from the inner and outer Galaxy. We use the angular momentum of each star about the Galactic center to determine the guiding center radius and to eliminate the effects of epicyclic motion, which would otherwise blur the estimated gradients. We interpret the effective temperature as a proxy for mean age, and conclude that the decreasing gradient is consistent with the predictions of radial mixing due to transient spiral patterns. We find some evidence that the trend of decreasing gradient with increasing mean age breaks to a constant gradient for samples of stars whose main-sequence life-times exceed the likely age of the thin disk.