Dark Matter Halo Sparsity of Modified Gravity Scenarios

TL;DR

This paper explores how modified gravity models affect the internal mass distribution of galaxy clusters, using halo sparsity as a probe, and discusses the potential for future measurements to test these models.

Contribution

It demonstrates that halo sparsity evolution can reveal signatures of modified gravity and assesses the observational prospects for testing MG scenarios with future data.

Findings

Screening mechanisms leave distinct signatures in sparsity evolution.

Current mass uncertainties hinder testing MG models.

Future large cluster samples could enable testing MG with better mass accuracy.

Abstract

Modified Gravity (MG) scenarios have been advocated to account for the dark energy phenomenon in the universe. These models predict departures from General Relativity on large cosmic scales that can be tested through a variety of probes such as observations of galaxy clusters among others. Here, we investigate the imprint of MG models on the internal mass distribution of cluster-like halos as probed by the dark matter halo sparsity. To this purpose we perform a comparative analysis of the properties of the halo sparsity using N-body simulation halo catalogs of a standard flat $\Lambda$CDM model and MG scenarios from the DUSTGRAIN-pathfinder simulation suite. We find that the onset of the screening mechanism leaves a distinct signature in the redshift evolution of the ensemble average halos sparsity. Measurements of the sparsity of galaxy clusters from currently available mass estimates are unable to test MG models due to the large uncertainties on the cluster masses. We show that this should be possible in the future provided large cluster samples with cluster masses determined to better than $30\%$ accuracy level.