Radiative Transfer in H II Regions.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radiative Transfer in H II Regions. Rubin, Robert H. Abstract Two aspects of the transfer of radiation which affect the structure and emission properties of H II regions are considered: the transfer of ionizing radiation produced by recombinations and the transfer of radiation in far infrared forbidden lines under optically thick conditions. Xumerical methods are used to solve the equations of ionization and thermal equilibrium for gaseous nebulae, allowing for an arbitrary density distribution. Absorption of ionizing photons by H and He is included, and ions of 0, X, Xe, and C are considered as forbidden line coolants. It is shown that the "on the spot" absorption approximation (Zanstra, Bull. Astron. Inst. Neth. 11, 341, 1951) can cause considerable error in the temperature structure and predicted emission properties. Models calculated using detailed solutions for the transfer of diffuse Lyman continuum radiation show that the temperature near the center may be increased by 20000K. It is also demonstrated that certain of the far infrared forbidden lines of the cooling ions undergo considerable self-absorption. The optical thickness for two of these lines, the 88 ~ and 52 ~ lines of O++, which are among the most efficient nebular coolants (Hjellming, Astrophys. J. 143, 420,1966) decreases their cooling efficiency, raising temperatures up to 500-10000K. A discussion of the predicted surface brightness in the important lines is discussed in the light of these results. Publication: The Astronomical Journal Pub Date: October 1967 DOI: 10.1086/110515 Bibcode: 1967AJ.....72R.825R full text sources ADS |