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A Possible Evolutionary Feature in the Spectra of Radio Galaxies

Published online by Cambridge University Press:  14 August 2015

O. B. Slee
O. B. Slee*
Affiliation:
Division of Radiophysics, CSIRO, Sydney, Australia

Extract

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A recent analysis (Slee, 1981) of the spectra of extragalactic sources derived by Slee et al. (1981) has revealed a relationship between spectral index and redshift in the sense that the spectra of identified radio galaxies steepen with increasing redshift; this behaviour is consistent with an effect first reported by Kellermann et al. (1969) that the average spectral index of identified radio galaxies is lower than that of sources in empty optical fields, which are now generally regarded as distant radio galaxies (rather than QSOs). However, because of the selection effects present in the sample, Slee was not able to decide whether the basic correlation is between spectral index and redshift (implying an evolutionary origin), between spectral index and radio power, or between spectral index and linear dimension.

Type
Research Article
Information
Symposium - International Astronomical Union , Volume 97: Extragalactic Radio Sources , 1982 , pp. 35 - 38
Copyright
Copyright © Reidel 1982 

References

Kellermann, K.I.: 1966, Astrophys. J. 146, p. 621.Google Scholar
Kellermann, K.I., Pauliny-Toth, I.I.K. and Williams, P.J.S.: 1969, Astrophys. J. 157, p. 1.Google Scholar
Melrose, D.B.: 1980, In ‘Plasma Astrophysics’, Vol. 2, p. 106, Gordon & Breach.Google Scholar
Slee, O.B.: 1981, ‘Some features in the spectra of extragalactic radio sources’, Proc. Astron. Soc. Aust. (in press).Google Scholar
Slee, O.B., Siegman, Betty C. and Mulhall, P.S.: 1981, ‘Spectra, dimensions and luminosities of radio sources in the Culgoora-3 list’, Proc. Astron. Soc. Aust. (in press).Google Scholar