CLUMP-3D. Testing $\Lambda$CDM with galaxy cluster shapes

TL;DR

This study tests the $\Lambda$CDM model by comparing predicted and observed three-dimensional shapes of galaxy clusters using a multi-probe analysis, finding consistency with theoretical predictions and providing insights into baryonic effects.

Contribution

It introduces a comprehensive 3D analysis combining multiple observational probes to test $\Lambda$CDM predictions on galaxy cluster shapes.

Findings

Cluster shapes and concentrations match $\Lambda$CDM predictions.

Clusters are randomly oriented, consistent with selection criteria.

Shapes align with DM-only simulations, suggesting limited baryonic impact.

Abstract

The $\Lambda$CDM model of structure formation makes strong predictions on concentration and shape of DM (dark matter) halos, which are determined by mass accretion processes. Comparison between predicted shapes and observations provides a geometric test of the $\Lambda$CDM model. Accurate and precise measurements needs a full three-dimensional analysis of the cluster mass distribution. We accomplish this with a multi-probe 3D analysis of the X-ray regular CLASH (Cluster Lensing And Supernova survey with Hubble) clusters combining strong and weak lensing, X-ray photometry and spectroscopy, and the Sunyaev-Zel'dovich effect. The cluster shapes and concentrations are consistent with $\Lambda$CDM predictions. The CLASH clusters are randomly oriented, as expected given the sample selection criteria. Shapes agree with numerical results for DM-only halos, which hints at baryonic physics being not so effective in making halos rounder.