Baryons at the Edge of the X-ray Brightest Galaxy Cluster

TL;DR

This study uses Suzaku X-ray data to accurately measure the distribution of gas, metals, and dark matter in the Perseus Cluster's outskirts, revealing a baryon fraction consistent with cosmological expectations up to half the virial radius and indicating gas clumpiness at larger radii.

Contribution

First detailed spatially resolved census of baryons, metals, and dark matter at the outskirts of a galaxy cluster using Suzaku data, challenging previous findings.

Findings

Baryon fraction matches universal value at half the virial radius.

Baryon fraction exceeds cosmic mean at larger radii, indicating gas clumpiness.

Results inform understanding of cluster growth from the cosmic web.

Abstract

Studies of the diffuse X-ray emitting gas in galaxy clusters have provided powerful constraints on cosmological parameters and insights into plasma astrophysics. However, measurements of the faint cluster outskirts have become possible only recently. Using data from the Suzaku X-ray telescope, we determined an accurate, spatially resolved census of the gas, metals, and dark matter out to the edge of the Perseus Cluster. Contrary to previous results, our measurements of the cluster baryon fraction are consistent with the expected universal value at half of the virial radius. The apparent baryon fraction exceeds the cosmic mean at larger radii, suggesting a clumpy distribution of the gas, which is important for understanding the ongoing growth of clusters from the surrounding cosmic web.