Physical Processes in Active Galactic Nuclei

Abstract

Active Galactic Nuclei (henceforth AGN) have been observed assiduously, throughout the electromagnetic spectrum over the past 30 years and we know much about their collective and individual properties. Unfortunately, we are still a long way from being sure how they work. My primary intention, in the lectures that follow, is to explain some of the most important mechanisms that are believed to operate in these objects to an audience with a graduate physics and general astronomical background, but little prior exposure to AGN. In this way, I hope to provide a "toolkit" useful for understanding the abundance of models that have already been proposed to interpret the observations that will be reviewed more systematically here by Drs. Netzer and Woltjer. I shall make no attempt to summarize the phenomenology of AGN; neither will I give a critique of the models, although some personal preferences will clearly emerge, especially in the final lecture in which I outline one possible unified interpretation of AGN. I shall, however, draw upon both observations and models selectively to illustrate these physical processes. In the interests of brevity, I can only give heuristic derivations of most of the physical processes that I shall discuss. However, when possible, I will give more accurate formulae and references to their derivation.