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Evidence for a quasar in the radio galaxy Cygnus A from observation of broad-line emission

Nature volume 371, pages 313–314 (1994)Cite this article

Abstract

ACTIVE galaxies are thought to be powered by the accretion of surrounding dust and gas onto central black holes. The unified model1–3 of active galaxies predicts that narrow-line radio galaxies (NLRGs), which are very luminous at radio wavelengths and have narrow optical emission lines, would appear as quasars—which have broad emission lines—if viewed from a different direction. The nearby NLRG Cygnus A is the most luminous radio source in the local Universe, with a luminosity that lies within the range of that of quasars4, but the polarization of optical light from this source seems at odds with the quasar model. Here we present evidence, in the form of broad ultraviolet line emission from singly ionized magnesium, that Cygnus A does indeed host a quasar.

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Authors and Affiliations

  1. Physics Department, University of California at Santa Barbara, Santa Barbara, California, 93106, USA

    Robert Antonucci & Todd Hurt

  2. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland, 21218, USA

    Anne Kinney

Authors
  1. Robert Antonucci
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  2. Todd Hurt
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  3. Anne Kinney
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Antonucci, R., Hurt, T. & Kinney, A. Evidence for a quasar in the radio galaxy Cygnus A from observation of broad-line emission. Nature 371, 313–314 (1994). https://doi.org/10.1038/371313a0

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