The dynamics of radiation-pressure-dominated H II regions

Abstract

We evaluate the role of radiation pressure in the dynamics of H II regions. We first determine under what conditions radiation pressure is significant in comparison to gas pressure and show that, while radiation pressure is generally unimportant for H II regions driven by a handful of massive stars, it is dominant for the larger H II regions produced by the massive star clusters found near the Galactic center and in starburst environments. We then provide a solution for the problem of how H II regions expand when radiation pressure influences their behavior. Finally, we compare radiation-dominated H II regions to other sources of stellar feedback, and argue that H II regions are probably the primary mechanism for regulating the formation of massive star clusters. © 2009. The American Astronomical Society. All rights reserved..