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Physical Conditions in Radio Galaxies and Quasars

Published online by Cambridge University Press:  14 August 2015

Donald E. Osterbrock
Donald E. Osterbrock*
Affiliation:
Lick Observatory, Board of Studies in Astronomy and Astrophysics, University of California, Santa Cruz

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It is well known from the pioneering work of Baade and Minkowski that radio galaxies very often have strong emission lines in the spectra of their nuclei, indicating the presence of relatively large amounts of ionized gas. For instance, in the early survey of radio galaxies by Schmidt (1965), of the 35 galaxies observed, 32 had at least [0 II] λ3727 in their spectra and well over half had relatively strong [0 II] and other observable emission lines as well. In the recent review of optical identifications and spectroscopy of the revised 3C catalogue of radio sources by Smith et al. (1976), 137 radio galaxies are listed. Of these descriptive spectral information is given for 98, of which 49 show strong–emission line spectra, 19 intermediate–strength emission, 12 weak emission, and 18 a pure absorption–line spectrum without detectable emission lines. The fraction of objects with emission line–spectra is much higher than for normal galaxies. It is thus apparent that though the presence of emission lines is neither a necessary nor a sufficient condition that a galaxy be an observable radio source, nevertheless a large fraction of radio galaxies do contain ionized gas in their nuclei.

Type
IV. Optical Spectra and Identifications
Information
Symposium - International Astronomical Union , Volume 74: Radio Astronomy and Cosmology , 1977 , pp. 183 - 191
Copyright
Copyright © Reidel 1977 

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