Hardcastle, M. J.M. J.HardcastleCroston, J. H.J. H.CrostonShimwell, T. W.T. W.ShimwellTasse, C.C.TasseGürkan, G.G.GürkanMorganti, R.R.MorgantiMURGIA, MATTEOMATTEOMURGIARöttgering, H. J. A.H. J. A.Röttgeringvan Weeren, R. J.R. J.van WeerenWilliams, W. L.W. L.Williams2021-01-212021-01-2120190035-8711http://hdl.handle.net/20.500.12386/29930We 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.STAMPAenArticle10.1093/mnras/stz19102-s2.0-85082625320000485158400033https://academic.oup.com/mnras/article/488/3/3416/55313252019MNRAS.488.3416HFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_6 Stars and stellar systems