NGC 326: X-shaped no more

M. J. Hardcastle, J. H. Croston, T. W. Shimwell, C. Tasse, Gulay Gurkan Uygun, R. Morganti, M. Murgia, H. J. A. Rottgering, R. J. van Weeren, W. L. Williams

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)
21 Downloads (Pure)


We present new 144-MHz 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.
Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Early online date11 Jul 2019
Publication statusPublished - 1 Sept 2019


  • astro-ph.GA


Dive into the research topics of 'NGC 326: X-shaped no more'. Together they form a unique fingerprint.

Cite this