Jet termination in wide-angle tail radio sources

Abstract

Wide-angle tail radio galaxies (WATs) are an uncommon class of radio sources with luminosities near the FR I/FR II break, and are usually associated with central cluster galaxies. Their defining characteristic when imaged sensitively at high resolution is their twin, well-collimated jets, which can persist with low opening angle for tens of kiloparsecs before flaring into long, often bent, plumes. Although several models for the jet termination have been proposed, the majority of them are unsatisfactory when confronted with observations. Here we present the results of a programme of radio observations made with the aims of showing that objects classified as WATs do all have well-collimated jets and of seeing in detail how the jets disrupt as they enter the plumes. We show that compact, 'hotspot-like' features at the ends of the jets are common but by no means universal, and discuss the constraints that this places on models of the jet-plume transition. We discuss the properties of the observed well-collimated jets, and, using relativistic beaming models, estimate their speed to be ∼0.3c. Finally, we show that the distance from the galactic centre at which the base of the plume is found is related to the temperature of the host cluster.