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Excitation Mechanism of Extended Emission-Line Regions in Active Galaxies

Published online by Cambridge University Press:  12 April 2016

Ian Evans
Affiliation:
Smithsonian Astrophysical Observatory, 60 Garden Street, MS-27, Cambridge, MA 02138, USA
Anuradha Koratkar
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
Mark Allen
Affiliation:
The Johns Hopkins University, Department of Physics and Astronomy, 3200 Charles Street, Baltimore, MD 21218, USA
Zlatan Tsvetanov
Affiliation:
The Johns Hopkins University, Department of Physics and Astronomy, 3200 Charles Street, Baltimore, MD 21218, USA
Michael Dopita
Affiliation:
Mount Stromlo and Siding Spring Observatories, Weston PO, ACT 2611, Australia

Abstract

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Photoionization and shock models of the extended emissionline regions (EELRs) in active galaxies demonstrate that the optical emission lines alone are a poor discriminant of the excitation mechanism. Combining optical and UV data provides a discriminant between nuclear photoionization and autoionizing shock models. Hubble Space Telescope UV spectrophotometry of two Seyferts suggests that the EELRs in these objects are probably photoionized by the nucleus.

Type
VII. Shocks and Photoionization
Copyright
Copyright © Astronomical Society of the Pacific 1997

References

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