Physical Processes in Gaseous Nebulae. VIII. The Ultraviolet Radiation Field and Electron Temperature of an Optically Thick Nebula.

The theory of the transfer of radiation in the Lyman continuum that was developed in papers VI and VII of this series is applied to a numerical example. A central star radiating as a black body at a temperature of 80,0000 C. is assumed to illuminate a nebular shell whose optical thickness at the Lyman series limit is 3.0. The numerical methods of solution are discussed in detail. The redistribution of electron velocities by collisions and free-free transitions is shown to have considerable effect upon the char- acter of the radiation field. Near the series limit more radiation gets through the nebula than would otherwise be expected. The electron temperature at the inner boundary is almost that of an optically thin nebular shell, and at the outer boundary it approaches that of the central star