Dynamical HiiRegion Evolution in Turbulent Molecular Clouds

We present numerical radiation-hydrodynamic simulations of the evolution ofHII regions formed in an inhomogeneous medium resulting from turbulencesimulations. We find that the filamentary structure of the underlying densitydistribution produces a highly irregular shape for the ionized region, in whichthe ionization front escapes to large distances in some directions within80,000 years. In other directions, on the other hand, neutral gas in the formof dense globules persists within 1 parsec of the central star for the fullduration of our simulation (400,000 years). Divergent photoablation flows fromthese globules maintain a root-mean-squared velocity in the ionized gas that isclose to the ionized sound speed. Simulated images in optical emission linesshow morphologies that are in strikingly detailed agreement with those observedin real HII regions.