A pan spectral (theorist’s) view of star forming regions
When it became clear that an irradiated molecular cloud, the obscuring torus, was responsible for many of the observed properties of AGN, I decided to understand what happens when ionizing radiation strikes molecular gas. The nearest place where we can study this in detail is the Orion Nebula; M17 is the closest with a significant star cluster, and 30 Dor is the nearest starburst. Mechanical energy from the windy star cluster forms a bubble of hot gas that constitutes the base of the resulting structure. The optically-bright H II regions are interfaces between this hot gas and surrounding molecular gas. The starlight momentum compresses the atomic and molecular gas, increasing the magnetic field strength and pressure. The overall structure is in approximate magnetostatic equilibrium. This simple geometry provides a basis for making testable predictions for a number of relationships.