A detailed statistical analysis of the mass profiles of galaxy clusters

TL;DR

This study uses Bayesian analysis of X-ray data from 11 galaxy clusters to compare mass profile models, finding NFW as best among two-parameter models and evidence for a variable inner slope in three-parameter models.

Contribution

It provides a thorough Bayesian comparison of mass profile models for galaxy clusters, highlighting the potential need for a variable inner slope parameter.

Findings

NFW model is the best two-parameter fit.

A generalized three-parameter NFW model with a variable inner slope is statistically favored.

Mass-concentration relation aligns with numerical simulation predictions.

Abstract

The distribution of mass in the halos of galaxies and galaxy clusters has been probed observationally, theoretically, and in numerical simulations. Yet there is still confusion about which of several suggested parameterized models is the better representation, and whether these models are universal. We use the temperature and density profiles of the intracluster medium as measured by X-ray observations of 11 relaxed galaxy clusters to investigate mass models for the halo using a thorough Bayesian statistical analysis. We make careful comparisons between two- and three-parameter models, including the issue of a universal third parameter. We find that, of the two-parameter models, the NFW is the best representation, but we also find moderate statistical evidence that a generalized three-parameter NFW model with a freely varying inner slope is preferred, despite penalizing against the extra degree of freedom. There is a strong indication that this inner slope needs to be determined for each cluster individually, i.e. some clusters have central cores and others have steep cusps. The mass-concentration relation of our sample is in reasonable agreement with predictions based on numerical simulations.