Unification of AGNs, and the Starburst Hypothesis

There is now ample evidence for partial unification of (a) Seyfert 1 and Seyfert 2 galaxies, in terms of obscuring tori and orientation effects; (b) steep-spectrum (lobe dominated) radio quasars and flat-spectrum (core dominated) radio quasars, in terms of relativistic beaming and orientation effects; and (c) blazars, radio-loud quasars and broad-line radio galaxies, and narrow-line radio galaxies, in terms of obscuring tori, relativistic beaming, and orientation effects. Variants or subsets of these basic sets have also been proposed — e.g., BL Lac objects and Fanaroff-Riley (1974) Class I galaxies. Much of the observational evidence was discussed at this conference, primarily by Bob Fosbury, Clive Tadhunter, Neal Jackson, Thaisa Storchi-Bergmann, Paul Alexander, Paolo Padovani, Dave Axon, and Alec Boksenberg, as well as in several posters; it involves spectropolarimetry, superluminal motion, projected sizes, relative numbers of different objects, lobe depolarization asymmetry, the inverse-Compton limit, ionization cones, variability, and other phenomena. A reasonable conclusion is that unification schemes must be correct at least to some degree.