标题： 研究具有辐射低效核的强冷核、高光度星系团样本 显示英文标题

标题： Investigating a sample of strong cool core, highly-luminous clusters with radiatively-inefficient nuclei

摘要： 我们研究了一组强冷核、高光度（大多数L_x > 10^(45)erg/s）的星系团，其中中心活动星系核的平均喷流功率必须非常高，但没有检测到中心点状X射线源。利用钱德拉的独特空间分辨率，分析了包括A1835、A2204和最具有质量的冷核星系团之一RXCJ1504.1-0248在内的13个星系团样本。所有中心星系都存在射电源，表明活跃的星系核，并且没有明显的X射线点源。对于样本中的所有星系团，核的X射线总辐射亮度低于整个星系团的2%。大多数核在2-10keV的X射线亮度小于约10^(42)erg/s。我们探讨了这些星系团为何能拥有如此强烈的X射线亮度，内层星系际气体具有较短的辐射冷却时间，需要强大的能量反馈来平衡这种冷却，同时又具有如此辐射低效的核心。如果中心黑洞的质量约为10^9M_sol，则其功率超过爱丁顿亮度的百分之一，预计它们将是辐射高效的。只有当它们是超大质量（M_BH > 10^(10)M_sol）时，其行为才会类似于较低质量吸积黑洞。我们的研究重点在于根据上述问题定义的条件推导出星系团核的X射线性质，同时简要讨论可能的解决方案。 显示英文摘要

摘要： We present a study of strong cool core, highly-luminous (most with L_x > 10^(45) erg/s), clusters of galaxies in which the mean jet power of the central active galactic nucleus must be very high yet no central point X-ray source is detected. Using the unique spatial resolution of Chandra, a sample of 13 clusters is analysed, including A1835, A2204, and one of the most massive cool core clusters, RXCJ1504.1-0248. All of the central galaxies host a radio source, indicating an active nucleus, and no obvious X-ray point source. For all clusters in the sample, the nucleus has an X-ray bolometric luminosity below 2 per cent of that of the entire cluster. Most have a nucleus 2 - 10 keV X-ray luminosity less than about 10^(42) erg/s. We investigate how these clusters can have such strong X-ray luminosities, short radiative cooling-times of the inner intracluster gas requiring strong energy feedback to counterbalance that cooling, and yet have such radiatively-inefficient cores. If the central black holes have masses ~10^9M_sol then the power exceeds one per cent of the Eddington luminosity, and they are expected to be radiatively-efficient. Only if they are ultramassive (M_BH > 10^(10)M_sol), would their behaviour resemble that of lower mass accreting black holes. Our study focuses on deriving the nucleus X-ray properties of the clusters as defined in the above question, while briefly addressing possible solutions.