Impulsively Triggered Star Formation

Abstract

I review several different modes of impulsively triggered star formation, starting with star formation in turbulent molecular clouds, and exploring the origin of the clump mass function and the scaling relations between clump mass, radius and internal velocity dispersion. This leads to the identification of a critical ram pres-sure for triggering rapid star formation, and a reappraisal of the minimum mass for opacity-limited star formation. I also discuss star formation triggered by ex-panding nebulae (HII regions, stellar-wind bubbles and supernova remnants) and star formation triggered by a sudden increase in external pressure, including the formation of brown dwarves and planetary-mass objects in HII regions by photo-erosion of pre-existing prestellar cores. I conclude by describing simulations of interactions between protostellar discs in dense small-N clusters, and note that such interactions are an efficient means of creating low-mass companions