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 IR 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-IR emission. Assuming it lies on the local M– $\sigma$ relation, it has an Eddington accretion rate of $\lambda_{\rm EDD}\sim 0.014$ . 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.

中文翻译：

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PKS 2250–351：Abell 3936 中的一个巨大射电星系

我们对射电星系 PKS 进行了详细分析 $2250{-}351$ ，一个投影大小为 1.2 Mpc 的巨人，它的宿主星系和它的环境。我们使用来自默奇森宽场阵列、升级的巨型米波长射电望远镜、澳大利亚平方公里阵列探路者和澳大利亚望远镜紧凑阵列的无线电数据来模拟射流功率和年龄。光学和红外数据来自星系和质量组装 (GAMA) 调查，并提供有关宿主星系和环境的信息。GAMA 光谱证实 PKS $2250{-}351$ 位于 $z=0.2115$ 在不规则且可能不松弛的 Abell 3936 星团中。我们发现它的宿主是一个巨大的“红色和死亡”椭圆星系，恒星形成可以忽略不计，但在中红外发射中具有高度模糊的活跃星系核。假设它位于本地米– $\sigma$ 关系，它的爱丁顿吸积率为 $\lambda_{\rm EDD}\sim 0.014$ . 我们发现波瓣衍生的射流功率（时间平均测量）比热点衍生的射流功率（瞬时测量）大一个数量级。我们建议在观察到的无线电发射的整个生命周期内（ ${\sim} 300\,$ Myr），吸积已经从低效的平流主导模式转变为薄盘有效模式，这与喷射功率的降低一致。我们还认为不对称的无线电形态是由于它的环境，与 PKS 的宿主 $2250{-}351$ 位于阿贝尔 3936 星系最密集的西部。