3C-465 - DYNAMICS OF A WIDE-ANGLE-TAIL RADIO-SOURCE

High-resolution multi-frequency polarization observations of the wide-angle-tail radio source 3C 465 in Abell 2634 are used to investigate dynamical models of the source evolution. It is argued that the observed fine scale of the Faraday rotation originates within the radio-emitting regions rather than in the intervening intracluster medium. An approximate density of 500 m-3 is derived for the radio components, similar to the density of the intracluster medium derived from X-ray observations. For a wide range of dynamical models, a minimum jet velocity of 3000 km s-1 is required to supply the total energy of the source over its spectral lifetime of ≈2 × 108 yr. Conventional models for the curved shape of the source involving buoyancy or ram pressure are shown to be unlikely. An alternative model is proposed, in which most of the extended structure remains static in the intracluster medium after having been deposited by fast jets. Radial velocity and morphological data for the associated D galaxy, NGC 7720, are shown to be consistent with the required velocity of several hundred km s-1. It is suggested that this kind of structure is the natural outcome if the motion of the central galaxy of a proto-classical-double carries the beams outside the radio lobes. The gradual closing of the gap between the hotspots after this event may explain part of the correlation between source power and gap width found by Birkinshaw et al. © 1984 Royal Astronomical Society.