Sloshing cold fronts in clusters, produced as the dense cluster core moves around in the cluster potential in response to in-falling subgroups, provide a powerful probe of the physics of the intracluster medium and the magnetic fields permeating it1,2. These sharp discontinuities in density and temperature rise gradually outwards with age in a characteristic spiral pattern, embedding into the intracluster medium a record of the minor merging activity of clusters: the further from the cluster centre a cold front is, the older it is. Recently, it was discovered that these cold fronts can survive out to extremely large radii in the Perseus cluster3. Here, we report on high-spatial-resolution Chandra observations of the large-scale cold front in Perseus. We find that rather than broadening through diffusion, the cold front remains extremely sharp (consistent with abrupt jumps in density) and instead is split into two sharp edges. These results show that magnetic draping can suppress diffusion for vast periods of time—around ~5 Gyr—even as the cold front expands out to nearly half the cluster virial radius.
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S.A.W. was supported by an appointment to the National Aeronautics and Space Administration Postdoctoral Program at the Goddard Space Flight Center, administered by the Universities Space Research Association through a contract with the National Aeronautics and Space Administration. A.F. acknowledges support from European Research Council Advanced Grant FEEDBACK.
The authors declare no competing interests.
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Walker, S.A., ZuHone, J., Fabian, A. et al. The split in the ancient cold front in the Perseus cluster. Nat Astron 2, 292–296 (2018). https://doi.org/10.1038/s41550-018-0401-8
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