The hydrodynamics of photoionized flows

We are working to bring together the ingredients necessary for a complete description of both the microphysics and the hydrodynamics of plasmas, allowing a self-consistent treatment of emission line regions such as those found in Galactic H II regions like Orion, extragalactic H II regions and luminous starburst galaxies. We are incorporating the necessary hydrodynamics into Cloudy, a plasma emission code that includes the physics needed to simulate the ionized, atomic, and molecular phases of the environment. The hydrodynamical flow, from the molecular cloud through the PDR into the H II region, brings advection terms into the thermal and ionization balance allowing both the H II region and PDR to be treated self-consistently. This will enable us to fully exploit the mid to far IR spectrum to understand the chemical evolution of the host system as well as star formation on many scales. Our first applications are to Orion, the best observed of these systems.