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