Cloud-cloud collisions and triggered star formation

TL;DR

This paper reviews recent observational and theoretical progress on how cloud-cloud collisions can trigger star formation, especially in forming massive stellar clusters and starbursts in galaxies.

Contribution

It provides a comprehensive review of recent findings and theories on cloud-cloud collision-induced star formation and discusses future research directions.

Findings

Cloud-cloud collisions are linked to massive cluster formation in galaxies.

Recent observations support collision-triggered star formation in various regions.

Theoretical models are advancing understanding of mass compression in collisions.

Abstract

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.