We present a detailed analysis of the radio galaxy PKS 2250 - 351 , a giant of 1.2 Mpc projected size , its host galaxy , and its environment .
We use radio data from the Murchison Widefield Array , the upgraded Giant Metre-wavelength Radio Telescope , the Australian Square Kilometre Array Pathfinder , and the Australia Telescope Compact Array to model the jet power and age .
Optical and infra-red data come from the Galaxy And Mass Assembly ( GAMA ) survey and provide information on the host galaxy and environment .
GAMA spectroscopy confirms that PKS 2250 - 351 lies at z = 0.2115 in the irregular , and likely unrelaxed , cluster Abell 3936 .
We find its host is a massive , ‘ red and dead ’ elliptical galaxy with negligible star formation but with a highly obscured active galactic nucleus dominating the mid-infrared emission .
Assuming it lies on the local M - \sigma relation it has an Eddington accretion rate of \lambda _ { EDD } \sim 0.014 .
We find that the lobe-derived jet power ( a time-averaged measure ) is an order of magnitude greater than the hotspot-derived jet power ( an instantaneous measure ) .
We propose that over the lifetime of the observed radio emission ( \sim 300 Myr ) the accretion has switched from an inefficient advection dominated mode to a thin-disc efficient mode , consistent with the decrease in jet power .
We also suggest that the asymmetric radio morphology is due to its environment , with the host of PKS 2250 - 351 lying to the west of the densest concentration of galaxies in Abell 3936 .