Mass modelling of galaxy clusters via velocity moments

TL;DR

This paper presents a method for galaxy cluster mass modeling using velocity moments, breaking degeneracies with kurtosis, and confirms the mass-concentration relation through application to real clusters.

Contribution

The paper introduces a novel approach combining velocity dispersion and kurtosis to accurately estimate galaxy cluster parameters, confirming simulation predictions.

Findings

Successfully applied to over 20 clusters.

Confirmed the mass-concentration relation.

Reliable recovery of halo properties from mock data.

Abstract

We summarize the method of mass modelling of galaxy clusters based on reproducing the dispersion and kurtosis of the projected velocity distribution of galaxies. The models are parametrized within the framework of the NFW density profile, characterized by the virial mass and concentration, together with the constant anisotropy of galaxy orbits. The use of velocity dispersion alone does not allow to constrain all the three parameters from kinematic data due to the mass-anisotropy degeneracy. The degeneracy is broken by introducing the fourth velocity moment, the kurtosis. We tested the method based on fitting both moments on mock data sets drawn from simulated dark matter haloes and showed it to reproduce reliably the properties of the haloes. The method has been applied to estimate the mass, concentration and anisotropy of more than 20 clusters which allowed us to confirm, for the first time using kinematic data, the mass-concentration relation found in N-body simulations.