  We study the migration and resonant capture of planetesimals in a planetary
system consisting of a gaseous disc analogous to the primordial solar nebula
and a Neptune-like planet. Using a simple treatment of the drag force we find
that planetesimals are mainly trapped in the 3:2 and 2:1 resonances and that
the resonant populations are correlated with the gaseous drag strength in a
sense that the 3:2 resonant population increases with the stronger gaseous
drag, but the 2:1 resonant population does not. Since planetesimals can lead to
the formation of larger bodies similar to asteroids and Kuiper Belt Objects,
the gaseous drag can play an important role in the configuration of a planetary
system.
