The Dark Matter Distribution in the Central Regions of Galaxy Clusters

TL;DR

This study combines gravitational lensing and stellar velocity data to measure dark matter profiles in galaxy cluster centers, testing predictions of the CDM model.

Contribution

It provides the first precise measurements of dark matter inner slopes in clusters with radial arcs, directly comparing observations with CDM simulations.

Findings

Dark matter inner slopes are consistent with CDM predictions in some clusters.

Clusters with radial arcs allow precise inner slope measurements.

Results challenge or support the universality of dark matter halo profiles.

Abstract

Cosmological N-body simulations predict that dark matter halos should have a universal shape characterized by a steep, cuspy inner profile. Here we report on a spectroscopic study of six clusters each containing a dominant brightest cluster galaxy (BCG) with nearby gravitational arcs. Three clusters have both radial and tangential gravitational arcs, whereas the other three display only tangential arcs. We analyze stellar velocity dispersion data for the BCGs in conjunction with the arc redshifts and lens models to constrain the dark and baryonic mass profiles jointly. For those clusters with radial gravitational arcs we were able to measure precisely the inner slope of the dark matter halo and compare it with that predicted from CDM simulations.