Wide-angle tailed radio galaxies

Abstract

In this paper, the properties of a class of extragalactic radio sources associated with dominant cluster galaxies known as wide-angle tails (WATs) are reviewed. The mechanism responsible for forming and, in particular, bending these sources remains controversial nearly 10 years after their discovery. To gain possibly new insight into these radio galaxies, we divide them into three subclasses according to linear size. The smallest WATs are limited in size to the optical extent of the galaxies, are weaker in radio power, and may be bent by dynamic pressure as a result of motion of the radio galaxy about a second large galaxy or subcondensation of galaxies in the cluster. The large, 1-Mpc size WATs are associated with a single, dominant cD galaxy, have only sharp and irregularly placed bends in the jets, and probably interact with clouds in the cluster gas. The moderate-size, symmetrically bent WATs such as 3C 465 may bend and decollimate as a result of the passage of a jet through a sharp pressure gradient, which occurs within the halos of these galaxies.