Cloud-cloud collisions and triggered star formation
  Star formation is a fundamental process for galactic evolution. One issue
over the last several decades has been determining whether star formation is
induced by external triggers or is self-regulated in a closed system. The role
of an external trigger, which can effectively collect mass in a small volume,
has attracted particular attention in connection with the formation of massive
stellar clusters, which in the extreme may lead to starbursts. Recent
observations have revealed massive cluster formation triggered by cloud-cloud
collisions in nearby interacting galaxies, including the Magellanic system and
the Antennae Galaxies as well as almost all well-known high-mass star-forming
regions such as RCW 120, M20, M42, NGC 6334, etc., in the Milky Way.
Theoretical efforts are laying the foundation for the mass compression that
causes massive cluster/star formation. Here, we review the recent progress on
cloud-cloud collisions and triggered star-cluster formation and discuss the
future prospects for this area of research.
