Broadband properties of active galactic nuclei

Citation

Edelson, Richard (1987) Broadband properties of active galactic nuclei. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-09092008-113501

Abstract

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The broadband radio-infrared-optical-ultraviolet properties of active galactic nuclei are used to investigate the nature of the central engine and the surrounding environment. Optically selected quasars (which have [...] = [...]) and Seyfert 1 galaxies ([...] = [...]) tend to have relatively flat infrared spectra and low reddenings, while most Seyfert 2 galaxies ([...] = [...]) and other dusty objects have steep infrared spectra and larger reddenings. The infrared spectra of most luminous radio-quiet active galaxies turn over near [...]80 [...]. It appears that the infrared spectra of most quasars and luminous Seyfert 1 galaxies are dominated by unreprocessed radiation from a synchrotron self-absorbed source of order a light day across, about the size of the hypothesized accretion disk. Seyfert 2 galaxies and other reddened objects have infrared spectra which appear to be dominated by thermal emission from warm ([...]50 K) dust, probably in the disk of the underlying galaxy. A broad emission feature, centered near 5 [...], is present in many luminous quasars and Seyfert 1 galaxies.

Highly polarized objects ("blazars") can be strongly variable at far-infrared wavelengths over time scales of months. There is no conclusive evidence for far-infrared variations in normal (low-polarization) quasars or Seyfert galaxies, although low-level flickering (at the [...]30% peak-to-peak level) cannot be ruled out.

Seyfert galaxies tend to have steep radio spectra ([...]). The radio spectra of Seyfert 1 galaxies often flatten out near 2 cm. There is no significant difference in the mean radio luminosities of Seyfert 1 and 2 galaxies. There are of order 10[...] Seyfert galaxies/Gpc[...], most of which have 6 cm luminosities between 10[...] and 10[...] ergs/s and 60 [...] luminosities between 10[...] and 10[...] ergs/s. The Seyfert 2 galaxy radio luminosity function cuts off sharply below 10[...] ergs/s.

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