Jets from MRC 0600-399 bent by magnetic fields in the cluster Abell 3376

Galaxy clusters are known to harbour magnetic fields, the nature of which remains unresolved. Intra-cluster magnetic fields can be observed at the density contact discontinuity formed by cool and dense plasma running into hot ambient plasma(1,2), and the discontinuity exists(3) near the second-brightest galaxy(4), MRC 0600-399, in the merging galaxy cluster Abell 3376 (redshift 0.0461). Elongated X-ray emission in the east-west direction shows a comet-like structure that reaches the megaparsec scale(5). Previous radio observations(6,7) detected the bent jets from MRC 0600-399, moving in same direction as the sub-cluster, against ram pressure. Here we report radio(8,9) observations of MRC 0600-399 that have 3.4 and 11 times higher resolution and sensitivity, respectively, than the previous results(6). In contrast to typical jets(10,11), MRC 0600-399 shows a 90-degree bend at the contact discontinuity, and the collimated jets extend over 100 kiloparsecs from the point of the bend. We see diffuse, elongated emission that we name 'double-scythe' structures. The spectral index flattens downstream of the bend point, indicating cosmic-ray reacceleration. High-resolution numerical simulations reveal that the ordered magnetic field along the discontinuity has an important role in the change of jet direction. The morphology of the double-scythe jets is consistent with the simulations. Our results provide insights into the effect of magnetic fields on the evolution of the member galaxies and intra-cluster medium of galaxy clusters. Radio observations of the cluster Abell 3376, combined with numerical modelling, attribute the bent jets associated with the second-brightest galaxy in the cluster to an ordered magnetic field at the discontinuity.

Automated summary

The study explored radio observations of the galaxy cluster Abell 3376, focusing on the second-brightest galaxy MRC 0600-399, where jets were observed bending at a contact discontinuity with downstream flattening of the spectral index, indicating cosmic-ray reacceleration. The research reveals the significant role of an ordered magnetic field at the discontinuity in affecting the direction of jets, with results consistent with high-resolution numerical simulations.