T. Venturi et al., RADIO PROPERTIES OF THE SHAPLEY-CONCENTRATION - II - J1324-3138 - A REMNANT OF A RADIO GALAXY IN THE ABELL CLUSTER A3556, Monthly Notices of the Royal Astronomical Society, 298(4), 1998, pp. 1113-1122
In this paper we present a detailed study of the radio galaxy J1324-31
38, located at a projected distance of 2arcmin from the centre of the
Abell cluster of galaxies A3556, belonging to the core of the Shapley
Concentration, at an average redshift of z = 0.05. We have observed J1
324-3138 over a wide range of frequencies: at 327 MHz (VLA), 843 MHz (
MOST), and at 1376, 2382, 4790 and 8640 MHz (ATCA). Our analysis sugge
sts that J1324-3138 is a remnant of a tailed radio galaxy, in which th
e nuclear engine has switched off and the radio source is now at a lat
e stage of its evolution, confined by the intracluster gas. The radio
galaxy is not in pressure equilibrium with the external medium, as is
often found for extended radio sources in clusters of galaxies. We fav
our the hypothesis that the lack of observed polarized radio emission
in the source is a result of Faraday rotation by a foreground screen,
i.e. the source is seen through a dense cluster gas, characterized by
a random magnetic field. An implication of the head-tail nature of the
source is that J1324-3138 is moving away from the core of A3556 and t
hat, possibly, a major merging event between the core of A3556 and the
subgroup hosting J1324-3138 has already taken place.