The field of active galactic nuclei (AGNs) is exploding. From a narrow discipline dealing with massive active black holes (BHs) and their immediate surroundings, it now includes the host galaxies of such BHs, the correlated evolution of BHs and galaxies, and the physics of extremely energetic phenomena like γ-ray jets. More than 1000 articles are being published in refereed journals every year about this topic, and the numbers are still growing. The equivalent number in the mid-1970s was about 200.

This book, The Physics and Evolution of Active Galactic Nuclei, is an attempt to cover most of the central topics in this large field in a way that emphasizes the basic physics and the complex connections between AGNs and other astronomical objects. It grew from a graduate-level course taught at Tel Aviv University over many years and from numerous international schools on this topic where I participate as a lecturer, and it contains three main themes. The first is a comprehensive description of the more important physical processes associated with AGNs: the physics of photoionized gas; dust in AGNs; nonthermal processes; and various modes of accretion onto BHs, including accretion disks and accretion flows. The second is a detailed description of various subgroups of AGNs and the main components in individual sources. These include radio-loud and radio-quiet AGNs, type-I and type-II sources, LINERs, blazars, broad and narrow emission line regions, broad and narrow absorption lines, megamasers, dusty tori, and X-ray-emitting gas near the BH. The third part deals with the various connections, evolutionary and others, between BHs and their host galaxies, including star-forming galaxies.