Physical processes in extragalactic radio sources

This paper summarizes extensive observational studies of the closest ultraluminous radio galaxy Cygnus A. These data are used to test jet theory for powering the double-lobed radio emitting structures. Issues addressed include: (i) jet stability, confinement, composition, and velocity, (ii) the double shock structure for the jet terminus and the origin of multiple radio hotspots, (iii) the nature of filamentary structure in the radio lobes, and (iv) the hydrodynamic evolution of the radio lobes within a hot: cluster atmosphere. These data are also used to constrain models for relativistic particle acceleration and energy losses (Fermi acceleration and synchtotron aging), as well as to determine magnetic field strengths and morphologies in the radio source and in the surrounding intracluster medium. (C) 1998 American Institute of Physics.