The split in the ancient cold front in the Perseus cluster

TL;DR

This study uses high-resolution Chandra data to reveal that the large-scale cold front in the Perseus cluster remains sharply defined and split into two edges, demonstrating magnetic draping's role in suppressing diffusion over billions of years.

Contribution

It provides new evidence that magnetic draping can maintain cold front sharpness and split into two edges at large radii, extending understanding of ICM physics.

Findings

Cold front remains extremely sharp and split into two edges.

Magnetic draping suppresses diffusion for about 5 Gyr.

Cold front extends nearly half the cluster virial radius.

Abstract

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 (ICM), and the magnetic fields permeating it. 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 has been discovered that these cold fronts can survive out to extremely large radii in the Perseus cluster. 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) but 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.