Hostname: page-component-77c89778f8-sh8wx Total loading time: 0 Render date: 2024-07-21T03:26:10.554Z Has data issue: false hasContentIssue false
  • English
  • Français

Optical Spectra of Radio-Loud and Radio-Quiet Active Galactic Nuclei

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

Extract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Many radio galaxies have strong emission lines in their optical spectra. The fraction with such lines is much larger than in “normal” galaxies. Radio galaxies generally also have very bright nuclei; thus those with strong emission lines are similar in both respects to Seyfert galaxies. Hence radio and Seyfert galaxies are both generally considered to be similar physical objects: active galactic nuclei. Their observational properties show they are closely related to quasars (quasi-stellar radio sources) and (radio-quiet) QSOs. A short table of the space density of these objects, culled from many sources, chiefly Schmidt (1978) and Simkim, Su and Schwarz (1980) is given below. Although all the numbers are quite uncertain, there is no doubt that the radio-loud objects are relatively rare. With less certainty, it appears that the ratio of numbers of radio galaxies to Seyfert galaxies is about the same as the ratio of numbers of quasars to QSOs.

Type
Research Article
Information
Symposium - International Astronomical Union , Volume 97: Extragalactic Radio Sources , 1982 , pp. 369 - 371
Copyright
Copyright © Reidel 1982 

References

Cohen, R. D. and Osterbrock, D. E.: 1981, Ap. J. 243, 81.CrossRefGoogle Scholar
Collin-Souffrin, S., Dumont, S., Heidmann, N. and Joly, M.: 1980, Astr. Ap. 83, 190.Google Scholar
Collin-Souffrin, S., Joly, M., Heidmann, N. and Dumont, S.: 1979, Astr. Ap. 72, 93.Google Scholar
Gaskell, C. M.: 1981, Ph.D. Thesis, UCSC.Google Scholar
Grandi, S. A.: 1981, Ap.J. submitted.Google Scholar
Hine, R. G. and Longair, M. S.: 1979, M.N.R.A.S. 188, 111.CrossRefGoogle Scholar
Miley, G. K. and Miller, J. S.: 1979, Ap.J. (Letters) 228, L55.CrossRefGoogle Scholar
Netzer, H.: 1980, Ap. J. 236, 406.CrossRefGoogle Scholar
Peterson, B. M., Foltz, C. B. and Byard, P. L.: 1981, Ap.J. submitted.Google Scholar
Phillips, M. M.: 1978a, Ap.J. Supp. 38, 187.CrossRefGoogle Scholar
Phillips, M. M.: 1978b, Ap. J. 226, 736.CrossRefGoogle Scholar
Schmidt, M.: 1978, Phys. Scripta 17, 135.CrossRefGoogle Scholar
Simkin, S. M., Su, H. J. and Schwarz, M. P.: 1980, Ap. J. 237, 404.CrossRefGoogle Scholar
Wills, B. J., Netzer, H., Uomoto, A. K. and Wills, D.: 1980, Ap. J. 237, 319.CrossRefGoogle Scholar