The effects of HII regions

University Observatory/Excellence Cluster “Universe”, Munich, Germany

Abstract

Recent work on the effects of HII regions on giant molecular clouds (GMCs) and their embedded clusters is discussed. Although the dispersive effects of ionising radiation on clouds, particularly massive ones with high escape velocities, is rather modest, it is argued that it is still a vitally important process in the evolution of GMCs and clusters. It is able to drive turbulence on GMC scales, to set the optical emergence timescales of at last ∼ 10³ M_⊙ clusters, and has a strong influence on the large-scale energy and momentum input of supernovae by determining their detonation environments.