CLASH-VLT: The inner slope of the MACS J1206.2-0847 dark matter density profile

TL;DR

This study measures the dark matter density profile of galaxy cluster MACS J1206.2-0847, finding an inner slope consistent with LambdaCDM predictions, using galaxy velocities and advanced modeling techniques.

Contribution

It provides the first detailed dynamical measurement of the inner dark matter slope in this cluster, confirming theoretical predictions.

Findings

Inner slope gammadm=0.7 with uncertainties, consistent with simulations.

Total mass profile agrees with X-ray and lensing data.

Supports cold dark matter models with steep inner profiles.

Abstract

The inner slope (gammadm) of the dark matter (DM) density profile of cosmological halos carries information about the properties of DM and/or baryonic processes affecting the halo gravitational potential. Cold DM cosmological simulations predict steep inner slopes, gammadm~1. We test this prediction on the MACS J1206.2-0847 cluster at redshift z=0.44, whose DM density profile was claimed to be cored at the center. We determine the cluster DM density profile from 2 kpc from the cluster center to the virial radius (~2 Mpc), using the velocity distribution of ~500 cluster galaxies and the internal velocity dispersion profile of the Brightest Cluster Galaxy (BCG), obtained from VIMOS@VLT and MUSE@VLT data. We solve the Jeans equation of dynamical equilibrium using an upgraded version of the MAMPOSSt method. The total mass profile is modeled as a sum of a generalized-NFW profile that describes the DM component, allowing for a free inner slope of the density profile, a Jaffe profile that describes the BCG stellar mass component, and a non-parametric baryonic profile that describes the sum of the remaining galaxy stellar mass and of the hot intra-cluster gas mass. Our total mass profile is in remarkable agreement with independent determinations based on X-ray observations and strong lensing. We find gammadm=0.7 (-0.1 +0.2) (68\% confidence levels), consistent with predictions from recent LambdaCDM cosmological numerical simulations.