Study of giant radio galaxies.

Abstract

Within the framework of the beam model, we have deduced some basic physical parameters of the jets and hotspots associated with classical double radio sources, following a simple approach which is based on the assumptions that the hotspots radiate under the usual equipartition conditions and that they are roughly spherical in shape. For a sample of 10 bright hotspots and for the jets presumed to be feeding them, we have estimated the densities, bulk velocities, mass flow rates, and efficiencies of the jets. It is found that the bulk outflow velocity of the relativistic electrons present inside the hotspot increases with the jet velocity and attains a maximum value of 0.25c (Saripalli and Gopal-Krishna, 1985). A rather natural explanation is found for the known tendency of more prominent and compact hotspots to be associated with sources of higher luminosities. It is also argued that the maximum expected luminosities of hotspots are approximately 10?? and 3 × 10?? erg s?¹, respectively, for beam velocities of < 0.1c and ~c. However, the latter limit could be surpassed due to a possible breakdown of the assumption of spherical shape for the hotspots at such high luminosities, where their morphology could undergo a qualitative change and become slab-like (Gopal-Krishna).