Effects of dust on the structure of H II regions

Abstract

The effects of dust on the internal structure and observational parameters of H II regions are discussed. Absorption of Lyman continuum radiation by dust is shown to reduce the size of nebulae while modifying their ionizational and thermal structure. Detailed numerical models are constructed and calculated with a computer code which solves the ionization and thermal equations iteratively, while the radiative transfer is handled in a modified form of the ''outward only'' approximation. The integrated intensities of several of the strongest optical emission lines are given for several models as a function of dust optical depth. Radio intensities, for both line and continuum emission, were calculated, and the resulting recombination-line temperatures, He/sup +//H/sup +/ ratios, and continuum fluxes are presented.