为什么在“非冷核”星系团的中心会有强射电活动星系核?
Why are there strong radio AGNs in the center of "non-cool core" clusters?
摘要:
在X射线冷核中的射电活动星系核反馈被认为是重子结构演化的一个重要组成部分。然而,人们早就知道强射电活动星系核也存在于“非冷核”星系团中,这就提出了一个问题,即射电反馈是否总是需要一个X射线冷核。我们提出了一个系统的分析,152组和集群,以显示每个BCG与一个强大的无线电活动星系核有一个X射线冷核心。那些位于“非冷核”系统中心的强射电活动星系核实际上与典型半径小于5 kpc的小X射线冷核(我们称之为日冕)有关。小型日冕最有可能是ISM起源的,它们携带了足够的燃料来为无线电活动星系核提供动力。我们的研究结果表明,传统的冷芯/非冷芯二分法是过于简单。一个更好的替代方法是用封闭的X射线光度的冷核分布函数。我们的研究结果的其他影响也进行了讨论,包括简单的外推的密度分布推导邦迪吸积率的警告。
英文摘要:
Radio AGN feedback in X-ray cool cores has been proposed as a crucial ingredient in the evolution of baryonic structures. However, it has long been known that strong radio AGNs also exist in "noncool core" clusters, which brings up the question whether an X-ray cool core is always required for radio feedback. We present a systematic analysis of 152 groups and clusters to show that every BCG with a strong radio AGN has an X-ray cool core. Those strong radio AGNs in the center of the "noncool core" systems identified before are in fact associated with small X-ray cool cores with typical radii of < 5 kpc (we call them coronae). Small coronae are most likely of ISM origin and they carry enough fuel to power radio AGNs. Our results suggest that the traditional cool core/noncool core dichotomy is too simple. A better alternative is the cool core distribution function with the enclosed X-ray luminosity. Other implications of our results are also discussed, including a warning on the simple extrapolation of the density profile to derive Bondi accretion rate.
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