Data from: PKS 2250-351: A giant radio galaxy in Abell 3936

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 themid-IR emission. Assuming it lies on the local relation, it has an Eddington accretion rate of λ ∼ 0.014. We find that the lobe-derived jet power (a time-averaged measure) is an order ofmagnitude greater than the hotspot-derived jet power (an instantaneousmeasure). We propose that over the lifetime of the observed radio emission ∼300 Myr), the accretion has switched from an inefficient advection-dominatedmode 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.

本研究针对射电星系（radio galaxy）PKS 2250.351、其宿主星系及其所处环境展开详尽分析。该射电星系为投影尺寸达1.2百万秒差距（Mpc）的巨型源。本研究使用默奇森宽场阵列（Murchison Widefield Array）、升级型巨型米波射电望远镜（upgraded Giant Metre-wavelength Radio Telescope）、澳大利亚平方公里阵列探路者（Australian Square Kilometre Array Pathfinder）以及澳大利亚望远镜紧凑阵列（Australia Telescope Compact Array）的射电观测数据，对喷流功率与年龄进行建模分析。光学与红外波段数据取自星系与质量组装巡天（Galaxy And Mass Assembly, GAMA），该巡天数据可用于获取宿主星系与所处环境的相关信息。GAMA光谱观测证实，PKS 2250.351位于红移值z=0.2115的不规则星系团阿贝尔3936（Abell 3936）中，该星系团大概率尚未达到弛豫状态。研究发现其宿主星系为大质量的“红死”椭球星系，恒星形成活动可忽略不计，但存在一个被严重遮蔽的活动星系核（active galactic nucleus, AGN），主导了其中红外波段的辐射。假设该宿主星系符合局域关系，其爱丁顿吸积率（Eddington accretion rate）λ约为0.014。研究发现，由射电瓣推导得到的喷流功率（一种时间平均测量量）比由射电热斑推导得到的喷流功率（一种瞬时测量量）高出一个数量级。我们提出，在本次观测到的射电辐射的寿命（约300百万年，Myr）内，吸积模式已从低效的径移主导模式转变为薄盘高效模式，这与喷流功率的下降趋势相一致。我们还提出，该射电源的非对称形态源于其所处的环境：PKS 2250.351的宿主星系位于阿贝尔3936中星系密度最高区域的西侧。