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Composite Models: A Tool for Interpreting the Emission-Line Spectra of Active Galactic Nuclei

Published online by Cambridge University Press:  07 August 2017

S.M. Viegas-Aldrovandi
Affiliation:
Department of Physics, The Ohio State University, USA
M. Contini
Affiliation:
School of Physics and Astronomy, Tel-Aviv University, Israel

Extract

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In the last decade, emission-lines from a large number of active galactic nuclei (AGN) have been observed. Most of the models built to explain the observed narrow emission-lines are based on photoionization. Although these photoionization models account for the observed general features, many points remain unexplained and several authors suggest an additional energy source (Ferland and Mushotzky 1984, Ferland and Osterbrock 1986, Stasinska 1984, Viegas-Aldrovandi and Gruenwald 1988). Another possible explanation is suggested by the emitting cloud motions, which account for the observed line widths. If the clouds are moving throughout a dilute gas (n0 ≃ 300 cm−3), a shock can develop. Then, the physical conditions in the cloud are determined by the coupled effect of photoionization and shock hydrodynamics.

Type
Part 5: Structure of the Central Object and NLR
Copyright
Copyright © Kluwer 1989 

References

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