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Title:
A guideline to the interpretation of the narrow emission-line spectra of active galactic nuclei
Authors:
Viegas-Aldrovandi, S. M.; Contini, M.
Affiliation:
AA(Ohio State University, Columbus), AB(Tel Aviv University, Israel)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 339, April 15, 1989, p. 689-699. (ApJ Homepage)
Publication Date:
04/1989
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ACTIVE GALACTIC NUCLEI, EMISSION SPECTRA, LINE SPECTRA, SHOCK WAVES, ABUNDANCE, COSMIC GASES, H BETA LINE, PHOTOIONIZATION, SPECTRAL LINE WIDTH
DOI:
10.1086/167328
Bibliographic Code:
1989ApJ...339..689V

Abstract

Considering that the narrow emission-line region of active galactic nuclei (AGNs) is composed by clouds moving throughout a dilute gas, the emission line spectrum is calculated assuming the coupled effects of shock and photoionization. A comparison between the H-beta line produced by shock and by photoionization shows that these mechanisms could have comparable importance in determining the physical conditions. The contributions to H-beta are of the same order if the cloud velocity is not above 300 km/s and the ionization parameter is not greater than 10,000. Theoretical emission-line intensities are given for several lines, for a large range of the input parameters, in order to provide a practical method to analyze observational data. Comparison between theoretical and observed line ratios shows that the presence of shock must be considered when analyzing the emission-line spectrum of AGNs.

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