A complete view of the outskirts of the Coma cluster

TL;DR

This study provides a detailed, high-resolution thermodynamic profile of the Coma cluster's outskirts using X-ray and Sunyaev-Zel'dovich observations, revealing entropy variations and asymmetries linked to cosmic web filaments.

Contribution

It offers the first comprehensive azimuthally resolved thermodynamic mapping of the Coma cluster outskirts, integrating XMM-Newton and Planck data to analyze gas properties and filamentary accretion effects.

Findings

Entropy profile matches non-radiative simulations beyond $r_{500}$.

Detected entropy deficit in the southwest outskirts near a cosmic web filament.

Profiles become increasingly asymmetric in disturbed directions, aligning with simulation predictions.

Abstract

We present a new extended XMM-Newton mosaic of the nearby Coma cluster, which covers the cluster out to the virial radius with nearly complete azimuthal coverage. This large mosaic is combined with the Planck Sunyaev Zel'dovich effect observations to recover the thermodynamic properties of the intracluster medium in an azimuthally averaged profile and 36 angular sectors, producing the highest spatial resolution view of the thermodynamics of the outskirts of a galaxy cluster in its entirety. Beyond $r_{500}$, our clumping corrected entropy measurements along the less disturbed directions are statistically consistent with the power-law entropy profile predicted by non-radiative simulations, and the gas mass fraction agrees with the mean cosmic baryon fraction. However, there is a clear entropy deficit in the outskirts to the southwest, coinciding with where Coma connects to a cosmic web filament which joins it to Abell 1367. The low entropy to the southwest extends from 0.5-1.0$r_{200}$, and is consistent with what is expected from simulations of a filamentary gas stream penetrating into the cluster as it continues to accrete matter from the cosmic web. We also find that the radial profiles of the recovered quantities become increasingly asymmetric in the outskirts, particularly along the more disturbed directions, consistent with the predictions of cosmological simulations.