Title: Brightest Cluster Galaxy Formation in the z=4.3 Protocluster SPT2349-56: Discovery of a Radio-Loud AGN Show Chinese title

Title: 最亮星系团星系在z=4.3原星系团SPT2349-56中的形成：发现一个射电明亮的AGN

Abstract: We have observed the z=4.3 protocluster SPT2349-56 with ATCA with the aim of detecting radio-loud active galactic nuclei (AGN) amongst the ~30 submillimeter galaxies identified in the structure. We detect the central complex of SMGs at 2.2\,GHz with a luminosity of L_2.2=(4.42pm0.56)x10^{25} W/Hz. The ASKAP also detects the source at 888 MHz, constraining the radio spectral index to alpha=-1.6pm0.3, consistent with ATCA non-detections at 5.5 and 9GHz, and implying L_1.4(rest)=(2.4pm0.3)x10^{26}W/Hz. This radio luminosity is about 100 times higher than expected from star formation, assuming the usual FIR-radio correlation, which is a clear indication of an AGN driven by a forming brightest cluster galaxy (BCG). None of the SMGs in SPT2349-56 show signs of AGN in any other diagnostics available to us (notably 12CO out to J=16, OH163um, CII/IR, and optical spectra), highlighting the radio continuum as a powerful probe of obscured AGN in high-z protoclusters. No other significant radio detections are found amongst the cluster members, consistent with the FIR-radio correlation. We compare these results to field samples of radio sources and SMGs, along with the 22 SPT-SMG gravitational lenses also observed in the ATCA program, as well as powerful radio galaxies at high redshifts. Our results allow us to better understand the effects of this gas-rich, overdense environment on early supermassive black hole (SMBH) growth and cluster feedback. We estimate that (3.3pm0.7)x10^{38} W of power are injected into the growing ICM by the radio-loud AGN, whose energy over 100Myr is comparable to the binding energy of the gas mass of the central halo. The AGN power is also comparable to the instantaneous energy injection from supernova feedback from the 23 catalogued SMGs in the core region of 120kpc projected radius. The SPT2349-56 radio-loud AGN may be providing strong feedback on a nascent ICM. Show Chinese abstract

Abstract: 我们使用ATCA观测了红移z=4.3的原星系团SPT2349-56，目的是在该结构中识别出约30个亚毫米波星系中的射电明亮活动星系核（AGN）。我们在2.2 GHz处检测到亚毫米波星系的中心复合体，其光度为L_2.2=(4.42±0.56)x10^{25} W/Hz。ASKAP也在888 MHz处检测到该源，限制了射电光谱指数为alpha=-1.6±0.3，与ATCA在5.5和9GHz处的非检测结果一致，并意味着L_1.4（rest）=(2.4±0.3)x10^{26}W/Hz。这种射电光度比假设通常的远红外-射电相关性下恒星形成预期的高约100倍，这明确表明由正在形成的最亮星系团星系（BCG）驱动的AGN。SPT2349-56中的任何亚毫米波星系都没有显示出其他诊断方法中AGN的迹象（特别是12CO延伸至J=16，OH163um，CII/IR和光学光谱），突显了射电连续谱作为高红移原星系团中被遮挡AGN的强大探测工具。在星系团成员中没有发现其他显著的射电检测，这与远红外-射电相关性一致。我们将这些结果与场样本的射电源和亚毫米波星系进行比较，以及与ATCA项目中观测到的22个SPT-SMG引力透镜，以及高红移处强大的射电星系进行比较。我们的结果使我们更好地理解这种气体丰富、密度高的环境对早期超大质量黑洞（SMBH）增长和星系团反馈的影响。我们估计，由射电明亮AGN注入生长中的ICM的功率为(3.3±0.7)x10^{38} W，在1亿年内的能量与中心晕气态质量的结合能相当。AGN的能量也与核心区域投影半径120kpc内23个已编目的亚毫米波星系的超新星反馈瞬时能量注入相当。SPT2349-56的射电明亮AGN可能正在对新生的ICM提供强烈的反馈。