Turbulence in the SuperModel: Mass Reconstruction with Nonthermal Pressure for Abell 1835

TL;DR

This paper introduces a SuperModel approach to account for nonthermal pressure in galaxy clusters, reconciling X-ray and lensing mass estimates and revealing baryons in outskirts.

Contribution

The study develops a SuperModel formalism that includes nonthermal pressure, improving mass reconstruction accuracy in galaxy clusters.

Findings

Including nonthermal pressure aligns X-ray mass with lensing estimates.

Reconstructed gas mass fraction matches cosmic value at virial radius.

Baryons are located in cluster outskirts, not missing.

Abstract

The total mass derived from X-ray emission is biased low in a large number of clusters when compared with the mass estimated via strong and weak lensing. Suzaku and Chandra observations out to the virial radius report in several relaxed clusters steep temperature gradients that on assuming pure thermal hydrostatic equilibrium imply an unphysically decreasing mass profile. Moreover, the gas mass fraction appears to be inconsistent with the cosmic value measured from the CMB. Such findings can be interpreted as an evidence for an additional nonthermal pressure in the outskirts of these clusters. This nonthermal component may be due to turbulence stirred by residual bulk motions of extragalactic gas infalling into the cluster. Here we present a SuperModel analysis of Abell 1835 observed by Chandra out to the virial radius. The SuperModel formalism can include in the equilibrium a nonthermal component whose level and distribution are derived imposing that the gas mass fraction f_{gas} equals the cosmic value at the virial radius. Including such a nonthermal component, we reconstruct from X rays an increasing mass profile consistent with the hydrostatic equilibrium also in the cluster outskirts and in agreement at the virial boundary with the weak lensing value. The increasing f_{gas} profile confirms that the baryons are not missing but located at the cluster outskirts.