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The difference between radio-loud and radio-quiet active galaxies
Wilson, A. S.; Colbert, E. J. M.
AA(University of Maryland, College Park, MD, US), AB(University of Maryland, College Park, MD, US)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 438, no. 1, p. 62-71 (ApJ Homepage)
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NASA/STI Keywords:
Active Galactic Nuclei, Black Holes (Astronomy), Luminosity, Radio Jets (Astronomy), Cosmology, Interacting Galaxies, Quasars, Radio Astronomy
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The recent development of unified theories of active galactic nuclei (AGNs) has indicated that there are two physically distinct classes of these objects--radio-loud and radio-quiet. Despite differences, the (probable) thermal emissions from the AGNs (continua and lines from X-ray to infrared wavelengths) are quite similar to the two classes of object. We argue that this last result suggests that the black hole masses and mass accretion rates in the two classes are not greatly different, and that the difference between the classes is associated with the spin of the black hole. We assume that the normal process of accretion through a disk does not lead to rapidly spinning holes and propose that galaxies (e.g., spirals) which have not suffered a recent major merger event contain nonrotating or only slowly rotating black holes. When two such galaxies merge, the two black holes are known to form a binary and we assume that they eventually coalesce. The ratio of the number of radio-loud to radio-quiet AGNs at a given thermal (e.g., optical) luminosity is determined by the galaxy merger rate. Comparisons between the predicted and observed radio luminosity functions constrain the efficiencies with which jet power is extracted from the spinning hole and radio emission is produced by the jet.

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