Physical Conditions in the Central Region, and the Nature of the Engine

Abstract

AbstractThe phenomena associated with Active Galactic Nuclei raise three main astrophysical problems: (1) the nature of the primary source of energy; (2) the physical conditions within the radiation source; (3) the nature of the population evolution over cosmological time-scales.I shall outline the links between (1) and (2), (1) and (3), that briefly go as follows. The Prime Mover is very likely to be a converter of gravitational energy in a very compact mass configuration. The associated radiation source, if it is also very compact, is so efficient and loss-dominated as to require specific conditions for the power transport and supply to the radiating particles: collisionless, effected by electromagnetic fields coherent on scales collective or macroscopic, to the point of producing at times anisotropic bulk motions. Very compact Prime Movers working at high regimes need also a compact mass supply; the output from these compound engines undergoes a characteristic change that accounts for the type of population evolutions of the associated sources.