Summary: Lecture 1
AGN Taxonomy and Unification
· Historical notes
· Multifrequency detection of nuclear activity
· Classification of AGN - taxonomy
· Evidence for obscuring tori in AGN
Itziar Aretxaga (INAOE) @El Escorial, Dec 2007
"Active" is used to refer to energetic processes that are not related to the
normal evolution of stars.
However, the nucleus of a galaxy is defined as an AGN when it has certain
optical spectroscopic characteristics. The definition does not address the
mechanism responsible for the peculiarities of the spectra.
AGN are a very
Seyfert galaxy: galaxy (usually a spiral) with a high surface brightness
nucleus that reveals unusual emission-lines (Seyfert 1943).