Clumpy ultracompact HII regions -- II. Cores, spheres and shells from subsonic flows
Abstract
We have modelled ultracompact HII regions (UCHIIR) in terms of steady subsonic ionized flows in a clumpy medium. Mass loss from neutral clumps allows the regions to be long-lived. We examine the form of global flows for different dependences of the volume mass injection rate, , on radius and Mach number, and describe the solutions in detail. We find that three observed UCHIIR morphologies are reproduced with these models. Mach number independent flows that include a radial variation can give centre- brightened core--halo morphologies. Mach number dependent flows reproduce naturally the uniform UCHIIR morphology. In a hybrid model, including subsonic and supersonic flows, we allow a supersonic 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 velocity structure very different from that of fully supersonic models. Several morphologies of spherical UCHIIR can be understood in terms of these various models; however, kinematic data are crucial as a discriminant between them.
Cite
@article{arxiv.astro-ph/9603002,
title = {Clumpy ultracompact HII regions -- II. Cores, spheres and shells from subsonic flows},
author = {M. P. Redman and R. J. R. Williams and J. E. Dyson},
journal= {arXiv preprint arXiv:astro-ph/9603002},
year = {2015}
}
Comments
6 pages with MN LaTeX macros, includes 12 postscript figures. Also available at http://axp2.ast.man.ac.uk:8000/Preprints.html