PHYSICAL PROCESSES IN EXTRAGALACTIC RADIO-SOURCES

This paper summarizes extensive observational studies of the closest u ltraluminous radio galaxy Cygnus A. These data are used to test jet th eory for powering the double-lobed radio emitting structures. Issues a ddressed include: (i) jet stability, confinement, composition, and vel ocity, (ii) the double shock structure for the jet terminus and the or igin of multiple radio hotspots, (iii) the nature of filamentary struc ture in the radio lobes, and (iv) the hydrodynamic evolution of the ra dio lobes within a hot: cluster atmosphere. These data are also used t o constrain models for relativistic particle acceleration and energy l osses (Fermi acceleration and synchtotron aging), as well as to determ ine magnetic field strengths and morphologies in the radio source and in the surrounding intracluster medium. (C) 1998 American Institute of Physics.