Radial Migration in Galactic Thick Discs

TL;DR

This study investigates how vertical motion influences radial migration of stars in galactic discs, finding that thick disc stars experience nearly as much angular momentum change as thin disc stars, with vertical action conserved during migration.

Contribution

It demonstrates that vertical motion only gradually reduces radial migration effects and highlights the conservation of vertical action over energy during the process.

Findings

Vertical motion slightly reduces angular momentum changes.

Thick disc stars undergo nearly as much migration as thin disc stars.

Vertical action, not energy, is conserved during migration.

Abstract

We present a study of the extent to which the Sellwood & Binney radial migration of stars is affected by their vertical motion about the midplane. We use both controlled simulations in which only a single spiral mode is excited, as well as slightly more realistic cases with multiple spiral patterns and a bar. We find that rms angular momentum changes are reduced by vertical motion, but rather gradually, and the maximum changes are almost as large for thick disc stars as for those in a thin disc. We find that particles in simulations in which a bar forms suffer slightly larger angular momentum changes than in comparable cases with no bar, but the cumulative effect of multiple spiral events still dominates. We have determined that vertical action, and not vertical energy, is conserved on average during radial migration.