Orbits of radial migrators and non-migrators around a spiral arm in
  N-body simulations
  Recent numerical N-body simulations of spiral galaxies have shown that spiral
arms in N-body simulations seem to rotate at a similar speed to the local
rotation speed of the stellar disc material. This in turn yields winding,
transient and recurrent spiral structure, whose co-rotating nature gives rise
to changes in the angular momentum (radial migration) of star particles close
to the spiral arm at many radii. From high resolution N-body simulations, we
highlight the evolution of strongly migrating star particles (migrators) and
star particles that do not migrate (non-migrators) around a spiral arm. We
investigate the individual orbit histories of migrators and non-migrators and
find that there are several types of migrator and non-migrator, each with
unique radial evolution. We contrast each type of orbit to establish the
reasons for the differences between them. We find that the positive (negative)
migrators sustain a position behind (in front of) the spiral arm, and feel
continuous tangential force as long as the spiral arm persists. On the other
hand, non-migrators stay close to the spiral arm, and pass or are passed by the
spiral arm one or two times. Although they gain or lose the angular momentum
when they are behind or in front of the spiral arm, their net angular momentum
change becomes close to zero. We discuss also the long term effects of radial
migration on the radial metallicity distribution and radial angular momentum
and mass profiles. [Abridged]
