NGC 326: X-shaped no more
NGC 326: X-shaped no more
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DOI：
10.1093/mnras/stz1910
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发表时间：
2019-07
影响因子：
4.8
通讯作者：
M. Hardcastle;J. Croston;T. Shimwell;T. Shimwell;C. Tasse;C. Tasse;G. Gurkan;R. Morganti;R. Morganti;M. Murgia;H. Röttgering;R. Weeren;W. Williams
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作者：
M. Hardcastle;J. Croston;T. Shimwell;T. Shimwell;C. Tasse;C. Tasse;G. Gurkan;R. Morganti;R. Morganti;M. Murgia;H. Röttgering;R. Weeren;W. Williams
我们展示了对典型的“x形”射电星系NGC 326的新的144 mhz低频阵列（LOFAR）观测结果，这些观测结果表明，以前已知的射电瓣翼平滑地延伸成一个大规模的、复杂的射电结构。我们认为这种结构很可能是正在进行的团或星团合并中的流体动力学效应的结果，对此已有的x射线和光学数据提供了独立的证据。这种大规模的射电结构很难仅仅从双黑洞合并导致的喷流重新定向的角度来解释，这是之前对NGC 326内部结构的一种解释。出于这个原因，我们建议最简单的模型是与合并相关的流体动力学过程解释所有源结构的模型，尽管我们不排除黑洞合并已经发生的可能性。在没有深入的、敏感的低频观测的情况下，从x形源的观测推断黑洞-黑洞合并率应该谨慎进行。一些x形的源可能是星团合并活动的标志，这将有助于更广泛地研究这些天体的环境。
We present new 144-MHz Low-Frequency Array (LOFAR) observations of the prototypical ‘X-shaped’ radio galaxy NGC 326, which show that the formerly known wings of the radio lobes extend smoothly into a large-scale, complex radio structure. We argue that this structure is most likely the result of hydrodynamical effects in an ongoing group or cluster merger, for which pre-existing X-ray and optical data provide independent evidence. The large-scale radio structure is hard to explain purely in terms of jet reorientation due to the merger of binary black holes, a previously proposed explanation for the inner structure of NGC 326. For this reason, we suggest that the simplest model is one in which the merger-related hydrodynamical processes account for all the source structure, though we do not rule out the possibility that a black hole merger has occurred. Inference of the black hole–black hole merger rate from observations of X-shaped sources should be carried out with caution in the absence of deep, sensitive low-frequency observations. Some X-shaped sources may be signposts of cluster merger activity, and it would be useful to investigate the environments of these objects more generally.