Radial migration in galactic disks caused by resonance overlap of multiple patterns: Self-consistent simulations

TL;DR

This paper demonstrates that resonance overlap of spiral and bar patterns significantly enhances radial migration in galactic disks, leading to rapid disk extension and metallicity gradient flattening, confirmed through self-consistent simulations.

Contribution

It provides the first self-consistent simulation evidence that resonance overlap between spiral and bar patterns drives efficient radial migration in galactic disks.

Findings

Resonance overlap causes bimodal angular momentum changes near bar resonances.

Gaseous components increase angular momentum exchange by about 20%.

Galactic disks can extend over 10 scale-lengths within 1-3 Gyr due to this mechanism.

Abstract

We have recently identified a new radial migration mechanism resulting from the overlap of spiral and bar resonances in galactic disks. Here we confirm the efficiency of this mechanism in fully self-consistent, Tree-SPH simulations, as well as high-resolution pure N-body simulations. In all barred cases we clearly identify the effect of spiral-bar resonance overlap by measuring a bimodality in the changes of angular momentum in the disk, dL, whose maxima are near the bar's corotation and outer Lindblad resonance. This contrasts with the smooth distribution of dL for a simulation with no stable bar present, where strong radial migration is induced by multiple spirals. The presence of a disk gaseous component appears to increase the rate of angular momentum exchange by about 20%. The efficiency of this mechanism is such that galactic stellar disks can extend to over 10 scale-lengths within 1-3 Gyr in both Milky Way size and low-mass galaxies (circular velocity ~100 km/s). We also show that metallicity gradients can flatten in less than 1 Gyr rendering mixing in barred galaxies an order of magnitude more efficient than previously thought.