Shocks in the Stacked Sunyaev-Zel'dovich Profiles of Clusters I: Analysis with the Three Hundred Simulations

TL;DR

This paper demonstrates that stacking thermal SZ profiles of galaxy clusters reveals shock features linked to accretion and splashback radius, providing new insights into cluster outskirts using simulations and upcoming surveys.

Contribution

It shows that shock features in SZ profiles can be detected through stacking and are correlated with cluster accretion rates and splashback radius, offering a new observational probe.

Findings

Shock features appear in stacked SZ profiles.

Shock features correlate with accretion rate and splashback radius.

Detectability of shocks with upcoming SZ surveys.

Abstract

Gas infalling into the gravitational potential wells of massive galaxy clusters is expected to experience one or more shocks on its journey to becoming part of the intracluster medium (ICM). These shocks are important for setting the thermodynamic properties of the ICM and can therefore impact cluster observables such as X-ray emission and the Sunyaev-Zel'dovich (SZ) effect. We investigate the possibility of detecting signals from cluster shocks in the averaged thermal SZ profiles of galaxy clusters. Using zoom-in hydrodynamic simulations of massive clusters from the Three Hundred Project, we show that if cluster SZ profiles are stacked as a function of $R/R_{200m}$, shock-induced features appear in the averaged SZ profile. These features are not accounted for in standard fitting formulae for the SZ profiles of galaxy clusters. We show that the shock features should be detectable with samples of clusters from ongoing and future SZ surveys. We also demonstrate that the location of these features is correlated with the cluster accretion rate, as well as the location of the cluster splashback radius. Analyses of ongoing and future surveys, such as SPT-3G, AdvACT, Simons Observatory and CMB-S4, that include gas shocks will gain a new handle on the properties and dynamics of the outskirts of massive halos, both in gas and in mass.