研究强冷核、具有辐射效率低的核的高亮度星系团样品
Investigating a sample of strong cool core, highly-luminous clusters with radiatively-inefficient nuclei
摘要：
本文研究了强冷核、高亮度（大部分L_x > 10^（45）erg/s）星系团，其中中心活动星系核的平均喷流功率必须很高，但没有探测到中心点X射线源。利用Chandra独特的空间分辨率，分析了13个星团的样本，包括A1835，A2204和最大的冷核星团之一RXCJ 1504.1 -0248。所有的中央星系都有一个射电源，表明有一个活跃的核，没有明显的X射线点源。对于样本中的所有星系团，原子核的X射线热光度低于整个星系团的2%。大多数的核能量为2 - 10 keV，X射线光度小于10^（42）erg/s。我们研究了这些星系团如何能够具有如此强的X射线光度，短的辐射冷却时间的内部气体需要强大的能量反馈来抵消冷却，但有这样的辐射效率低的核心。如果中心黑洞的质量约为10^9 M_sol，那么其能量超过爱丁顿光度的1%，并且它们被认为是辐射有效的。只有当它们是超大质量的（M_BH > 10^（10）M_sol）时，它们的行为才类似于低质量吸积黑洞。我们的研究重点是推导上述问题中定义的簇的核X射线性质，同时简要地讨论可能的解决方案。
英文摘要：
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.
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