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

¹ AIP, An der Sterwarte 16, 14482 Potsdam, Germany
² Observatoire Astronomique de Strasbourg, CNRS UMR 7550, 67000 Strasbourg, France
e-mail: ivan.minchev@astro.unistra.fr
³ AIfA, Universtät Bonn, 53121 Bonn, Germany
⁴ Observatoire de Paris, LERMA, 61 avenue de L’Observatoire, 75014 Paris, France
⁵ Observatoire de Paris-Meudon, GEPI, CNRS UMR 8111, 5 pl. Jules Janssen, 92195 Meudon, France
⁶ ARI, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead, CH41 1LD, UK

Received: 2 June 2010
Accepted: 7 December 2010

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, ΔL, whose maxima are near the bar’s corotation and outer Lindblad resonance. This contrasts with the smooth distribution of ΔL 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^-1). 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.