Energy Loss Mechanisms for Fast Particles

Abstract

Beams or jets of rapidly moving particles appear to be present in several classes of objects in astrophysics, including active galactic nuclei and quasars, compact binary systems, and supemovae. There is evidence from some radio bright active galaxies of a direct connection between the central, relativistically moving beams and the large, subrelativistic radio jets. In this paper we review the various energy loss mechanisms for a beam of relativistic particles propagating through an ambient medium, and compare the energy loss rate of those processes with that of plasma (collective) processes. Plasma processes are typically found to be the dominant energy loss mechanism. Inverse Compton X-ray emission and proton-proton related γ-ray production yield photons at roughly equal rates, and X-ray and γ-ray emission represent less than 10% of the total energy loss rate of the beams for parameters likely to be associated with the nuclei of active galaxies and quasars.