The NE III-O II forbidden-line spectrum as an ionization indicator in nebulae

Autor:	R. D. Blum, S. R. Cranmer, G. P. Tiede, R. I. Haefner, B. Ali, G. J. Ferland, T. E. Bumgardner
Rok vydání:	1991
Předmět:	Physics H II region chemistry.chemical_element Astronomy and Astrophysics Photoionization Mass spectrometry Neon chemistry Space and Planetary Science Ionization Orion Nebula Physics::Atomic Physics Emission spectrum Atomic physics Forbidden mechanism Astrophysics::Galaxy Astrophysics
Zdroj:	Publications of the Astronomical Society of the Pacific. 103:1182
ISSN:	1538-3873 0004-6280
DOI:	10.1086/132938
Popis:	The usefulness of the Ne III-O II forbidden-line spectrum as a helium ionization correction factor (ICF) indicator in low-density nebulae, such as H II regions, is examined, and the results of an extensive grid of photoionization simulations which have a 'blister'-like geometry are presented. Fully filled constant pressure gas, Orion dust, and H II region abundances are used, along with a very wide variety of ionizing continua. As suggested by the ionization potentials, the He ICF is small when the Ne III 3869/O II 3727 forbidden line ratio, an easily measured line pair, reaches above 0.20. The 'eta' parameter, a ratio of ratios of oxygen and sulfur lines, is probably strongly affected by low-temperature dielectronic recombination, a basic process which has no reliable rate coefficients for third-row elements.
Databáze:	OpenAIRE
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