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Astron. Astrophys. 336, 301-308 (1998)

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Diffuse radiation in models of photoionized nebulae

S.R. Och 1, L.B. Lucy 2 and M.R. Rosa * 2

1 Dr. Remeis-Sternwarte, Astronomisches Institut der Universität Erlangen-Nürnberg, Sternwartstrasse  7, D-96049 Bamberg, Germany,
2 Space Telescope-European Coordinating Facility, European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany (llucy@eso.org)

Received 20 December 1996 / Accepted 19 December 1997


This paper is the first in a series from a study of inhomogeneous gaseous nebulae, which has at its focus the apparent discrepancy between various observational aspects of real H II regions and theoretical predictions such as emission line ratios from low and high ionization species, details of the temperature structure and chemical abundance determination schemes. It is shown that the key problem is the detailed treatment of the radiation transport in an inhomogeneous and non-isotropic medium. We use a Monte Carlo technique, a proven means to handle complex radiation transport situations, to create photoionization models which are free of approximations concerning the radiative transfer. The code is tested for 1D homogeneous cases against the results from established photoionization codes, reaffirming its applicability to highly structured and non-symmetric nebulae.

Key words: ISM: H ii regions – radiative transfer – atomic processes – methods: numerical

* Affiliated to the Astrophysics Division of the Space Science Department of the European Space Agency (mrosa@eso.org)

Send offprint requests to: Michael R. Rosa

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© European Southern Observatory (ESO) 1998

Online publication: July 7, 1998