"Feedback from Star Formation and the Evolution of Giant Molecular Clouds"

Stars do not condense directly from the interstellar medium, but instead from massive dense clouds of molecular hydrogen. The internal motions of molecular clouds determines the masses, clustering properties, and formation rates of the stars they produce. Yet the underlying principles that govern these clouds' evolution remain controversial after half a century of research.

I argue that the mechanical feedback from forming stars dominates the energetics of molecular clouds. Protostellar jets have a disruptive effect on star and cluster-forming regions, but fail to explain the motions that supports giant clouds against gravity. This turbulence is sustained by massive stars, primarily through the formation of H II regions -- which also expel gas. I propose a self-consistent model in which giant molecular clouds form massive stars fast enough to sustain this turbulence, and decline in mass as a result. Finally, I explore the implications of this model for cloud lifetimes and for the mechanics of star formation in normal and starburst galaxies.