Collision of Merger and Accretion Shocks: Formation of Mpc-scale Contact Discontinuity in the Perseus Cluster

TL;DR

This paper proposes that large-scale contact discontinuities in the Perseus cluster result from the collision of accretion and merger shocks, offering an alternative to the common sloshing cold front explanation.

Contribution

It introduces a novel scenario where merger and accretion shock interactions create observed discontinuities, challenging previous interpretations.

Findings

Discontinuities may originate from shock collisions rather than gas sloshing.

The collision scenario explains the location and properties of observed structures.

Two discontinuities are linked to different shock interactions.

Abstract

Two Mpc-size contact discontinuities have recently been identified in the XMM-Newton and Suzaku X-ray observations of the outskirts of the Perseus cluster (Walker et al. 2020). These structures have been tentatively interpreted as "sloshing cold fronts", which are customarily associated with differential motions of the cluster gas, perturbed by a merger. In this study we consider an alternative scenario, namely, that the most prominent discontinuity near the cluster virial radius is the result of the collision between the accretion shock and the "runaway" merger shock. We also discuss the possible origin of the second discontinuity at ~1.2 Mpc.