“Zwicky's Nonet”：一个由9个星系和4C 35.06组成的紧凑合并系综，这是一个具有舞蹈无线电喷流的特殊无线电星系
`Zwicky's Nonet': a compact merging ensemble of nine galaxies and 4C 35.06, a peculiar radio galaxy with dancing radio jets
摘要：
本文报道了我们对位于Abell 407星系团（$z=0.047$）中心的一个扩展射电强活动星系核（4C~35.06）的射电、光学和红外研究结果。这个星系团的中心区域有一个由9个星系组成的非常紧密的系综，它们的光谱类似于被动红椭圆星系的光谱，镶嵌在一个$\sim$ 1~arcmin大小的弥散恒星晕中。这个系统（命名为“兹威基九号”）为多核cD星系的前身提供了独特而令人信服的证据。利用巨米波射电望远镜（GMRT）在610、235和150 MHz对4C~35.06进行了多频射电观测，发现了一个400 kpc尺度的螺旋形扭曲和扭结射电喷流以及外扩散瓣系统。喷流的外部末端包含非常陡峭的光谱（光谱指数-1.7到-2.5）遗迹/化石射电等离子体，光谱年龄为几个$\,\times (10^7 - 10^8)$年。这种没有明确热点的超陡频谱遗迹射电瓣是罕见的，它们提供了一个机会来了解相对论性喷流的生命周期和致密环境中黑洞合并的物理学。我们解释我们的观察，这个无线电源的背景下，其中央黑洞的增长，触发其活动星系核活动和喷旋，所有可能造成的星系合并在这个密集的星系系统。由于相互作用的黑洞之间的引力扰动的喷流轴的一个缓慢的圆锥进动被调用来解释不寻常的喷流形态。
英文摘要：
We report the results of our radio, optical and infra-red studies of a peculiar radio source 4C~35.06, an extended radio-loud AGN at the center of galaxy cluster Abell 407 ($z=0.047$). The central region of this cluster hosts a remarkably tight ensemble of nine galaxies, the spectra of which resemble those of passive red ellipticals, embedded within a diffuse stellar halo of $\sim$1~arcmin size. This system (named the `Zwicky's Nonet') provides unique and compelling evidence for a multiple-nucleus cD galaxy precursor. Multifrequency radio observations of 4C~35.06 with the Giant Meterwave Radio Telescope (GMRT) at 610, 235 and 150 MHz reveal a system of 400~kpc scale helically twisted and kinked radio jets and outer diffuse lobes. The outer extremities of jets contain extremely steep spectrum (spectral index -1.7 to -2.5) relic/fossil radio plasma with a spectral age of a few$\,\times (10^7 - 10^8)$ yr. Such ultra-steep spectrum relic radio lobes without definitive hot-spots are rare, and they provide an opportunity to understand the life-cycle of relativistic jets and physics of black hole mergers in dense environments. We interpret our observations of this radio source in the context of the growth of its central black hole, triggering of its AGN activity and jet precession, all possibly caused by galaxy mergers in this dense galactic system. A slow conical precession of the jet axis due to gravitational perturbation between interacting black holes is invoked to explain the unusual jet morphology.
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