Cold Fronts from Shock Collisions

TL;DR

This paper proposes that some cold fronts in galaxy clusters are caused by shock collisions, resulting in observable density and temperature discontinuities that can extend to the virial shock, supported by 1D simulations.

Contribution

It introduces a novel model linking shock collisions to cold front formation and demonstrates this with simulations showing concentric cold fronts tracing virial shock expansion.

Findings

Shock collisions produce density/temperature discontinuities of 1.4-2.7.

Cold fronts can be observed as far as the virial shock.

Simulations reveal concentric cold fronts from shock interactions.

Abstract

Cold fronts (CFs) are found in most galaxy clusters, as well as in some galaxies and groups of galaxies. We propose that some CFs are relics of collisions between trailing shocks. Such a collision typically results in a spherical, factor ~1.4-2.7 density/temperature discontinuity. These CFs may be found as far as the virial shock, unlike in other CF formation models. As a demonstration of this effect, we use one dimensional simulations where halo reverberations involving periodic collisions between the virial shock and outgoing secondary shocks exist. These collisions yield a distinctive, concentric geometric sequence of CFs which trace the expansion of the virial shock.