Radial Mixing due to Spiral-Bar Resonance Overlap: Implications to the Milky Way

TL;DR

This paper introduces a new radial migration mechanism caused by spiral and bar resonance overlap in galactic discs, which significantly impacts the Milky Way's structure and chemical distribution within a few billion years.

Contribution

It identifies a previously unknown, efficient radial mixing process due to resonance overlap, affecting galactic evolution models and constraints on bar and spiral structure longevity.

Findings

Rapid metallicity gradient flattening

Extended disc profile formation

Thick disc component emergence within a few Gyr

Abstract

We have recently identified a previously unknown radial migration mechanism resulting from the overlap of spiral and bar resonances in galactic discs (Minchev & Famaey 2010, Minchev et al. 2010). This new mechanism is much more efficient than mixing by transient spirals and its presence is unavoidable in all barred galaxies, such as our own Milky Way. The consequences of this are a strong flattening in the metallicity gradient in the disc, an extended disc profile, and the formation of a thick disc component, all taking place in only a couple of Gyr. This timescale is drastically shorter than previously expected and thus can put strong constraints on the longevity, strength and pattern speeds of the Galactic bar and Spiral Structure.