Low-ionization active galactic nuclei - X-ray or shock heated?

Abstract

view Abstract Citations (322) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Low ionization active galactic nuclei : X-ray or shock heated ? Halpern, J. P. ; Steiner, J. E. Abstract Some difficulties were experienced in connection with early photoionization models for the narrow-line regions of Seyfert galaxies. These difficulties could be overcome by the inclusion of charge transfer reactions. In connection with the present investigation, new photoionization models have been calculated for the forbidden-line regions, taking into account recent theoretical and observational developments. It is found that the entire range of excitation conditions observed in quasars, Seyfert galaxies, and 'Liners' (low-ionization nuclear emitting regions) can be reproduced by varying a single parameter which is related to the photon flux at the face of a cloud. There is some evidence that obscuration by the broad-line clouds may be responsible for the reduced flux seen by the narrow-line clouds in Liners and some low-luminosity Seyfert galaxies. It is shown that Einstein X-ray luminosities of several Liners and transition objects overlap with the weakest Seyfert galaxies. The implications of these findings for the classification of active galactic nuclei are discussed. Publication: The Astrophysical Journal Pub Date: June 1983 DOI: 10.1086/184051 Bibcode: 1983ApJ...269L..37H Keywords: Active Galactic Nuclei; Photoionization; Seyfert Galaxies; Shock Heating; X Ray Sources; Astronomical Models; Charge Transfer; Heao 2; Line Spectra; Luminosity; Astrophysics full text sources ADS | data products SIMBAD (15) NED (14)