A shock near the virial radius of the Perseus Cluster

TL;DR

This study presents evidence of a large-scale shock near the virial radius of the Perseus Cluster, identified through combined Suzaku X-ray observations revealing temperature and density discontinuities.

Contribution

The paper provides the first detailed analysis of a shock near the virial radius of a galaxy cluster using deep Suzaku data, advancing understanding of large-scale cluster growth.

Findings

Detection of a shock with Mach number 1.9 near r200

Discontinuities in emission measure and density profiles

First evidence of a virial shock at such large radius

Abstract

Previous X-ray studies of the Perseus Cluster, consisting of 85 Suzaku pointings along eight azimuthal directions, revealed a particularly steep decrease in the projected temperature profile near the virial radius (~r200) towards the northwest (NW). To further explore this shock candidate, another 4 Suzaku observations on the NW edge of the Perseus Cluster have been obtained. These deeper data were designed to provide the best possible control of systematic uncertainties in the spectral analysis. Using the combined Suzaku observations, we have carefully investigated this interesting region by analyzing the spectra of various annuli and extracting projected thermodynamic profiles. We find that the projected temperature profile shows a break near r200, indicating a shock with M = 1.9+-0.3. Corresponding discontinuities are also found in the projected emission measure and the density profiles at the same location. This evidence of a shock front so far away from the cluster center is unprecedented, and may provide a first insight into the properties of large-scale virial shocks which shape the process of galaxy cluster growth.