CLUMPY ULTRACOMPACT H-II REGIONS .2. CORES, SPHERES AND SHELLS FROM SUBSONIC FLOWS

We have modelled ultracompact HII regions (UCHIIR) in terms of steady subsonic ionized flows in a clumpy medium. Mass loss from neutral clum ps allows the regions to be long-lived. We examine the form of global flows for different dependences of the volume mass injection rate, q, on radius and Mach number, and describe the solutions in detail. We fi nd that three observed UCHIIR morphologies are reproduced with these m odels. Mach number independent flows that include a radial variation c an give centre- brightened core-halo morphologies. Mach number depende nt flows reproduce naturally the uniform UCHIIR morphology. In a hybri d model, including subsonic and supersonic flows, we allow a supersoni c wind to shock in the ionized region. The ionized subsonic gas has a high density and so dominates the emission. The shell produced has a v elocity structure very different from that of fully supersonic models. Several morphologies of spherical UCHIIR can be understood in terms o f these various models; however, kinematic data are crucial as a discr iminant between them.