2006/08/22 by Mark R. Krumholz, Christopher D. Matzner, Christopher F. McKee · 9 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Galaxy #Molecular cloud #Photoevaporation #Physics #Star formation #Stars #Stellar, planetary, and galactic studies #Virial theorem #astro-ph
paper · pdf · doi:10.1086/508679
published as Astrophys.J.653:361-382,2006 · Accepted for publication in ApJ. 25 pages, 8 figures, emulateapj format
arxiv created 2006/08/22 · openalex publication_date 2006/12/05 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present semianalytic dynamical models for giant molecular clouds evolving under the influence of H II regions launched by newborn star clusters. In contrast to previous work, we neither assume that clouds are in virial or energetic equilibrium, nor do we ignore the effects of star formation feedback. The clouds, which we treat as spherical, can expand and contract homologously. Photoionization drives mass ejection; the recoil of cloud material both stirs turbulent motions and leads to an effective confining pressure. The balance between these effects and the decay of turbulent motions through isothermal shocks determines clouds' dynamical and energetic evolution. We find that for realistic values of the rates of turbulent dissipation, photoevaporation, and energy injection by H II regions, the massive clouds where most molecular gas in the Galaxy resides live for a few crossing times, in good agreement with recent observational estimates that large clouds in Local Group galaxies survive roughly 20-30 Myr. During this time clouds remain close to equilibrium, with virial parameters of 1-3 and column densities near 10 22 H atoms cm -2 , also in agreement with observed cloud properties. Over their lives they convert 5%-10% of their mass into stars, after which point most clouds are destroyed when a large H II region unbinds them. In contrast, small clouds like those found in the solar neighborhood only survive ~1 crossing time before being destroyed.