Constraints on Radial Migration in Spiral Galaxies - II. Angular
  momentum distribution and preferential migration
  The orbital angular momentum of individual stars in galactic discs can be
permanently changed through torques from transient spiral patterns.
Interactions at the corotation resonance dominate these changes and have the
further property of conserving orbital circularity. We derived in an earlier
paper an analytic criterion that an unperturbed stellar orbit must satisfy in
order for such an interaction to occur i.e. for it to be in a trapped orbit
around corotation. We here use this criterion in an investigation of how the
efficiency of induced radial migration for a population of disc stars varies
with the angular momentum distribution of that population. We frame our results
in terms of the velocity dispersion of the population, this being an easier
observable than is the angular momentum distribution. Specifically, we
investigate how the fraction of stars in trapped orbits at corotation varies
with the velocity dispersion of the population, for a system with an assumed
flat rotation curve. Our analytic results agree with the finding from
simulations that radial migration is less effective in populations with
'hotter' kinematics. We further quantify the dependence of this trapped
fraction on the strength of the spiral pattern, finding a higher trapped
fraction for higher amplitude perturbations.
