The shape of the Chameleon fifth-force on the mass components of galaxy clusters

TL;DR

This paper develops a semi-analytical model of the Chameleon fifth-force in galaxy clusters, validating it against numerical solutions and demonstrating its potential to constrain modified gravity parameters using galaxy kinematics and BCG data.

Contribution

It introduces a semi-analytical chameleon field profile for galaxy cluster components and integrates it into a kinematic analysis tool, enabling new tests of modified gravity.

Findings

The semi-analytical profile matches numerical solutions accurately.

Galaxy kinematic data can constrain Chameleon gravity parameters.

Constraints are comparable to lensing+kinematics analyses.

Abstract

In the context of Chameleon gravity, we present a semi-analytical solution of the chameleon field profile in accurately modelled galaxy cluster's mass components, namely: the stellar mass of the Brightest Cluster Galaxy (BCG), the baryonic mass in galaxies (other than the BCG), the mass of the Intra-Cluster Medium (ICM) and the diffuse cold dark matter (CDM). The obtained semi-analytic profile is validated against the numerical solution of the chameleon field equation and implemented in the \textsc{MG-MAMPOSSt} code for kinematic analyses of galaxy clusters in modified gravity scenarios. By means of mock halos, simulated both in GR and in modified gravity, we show that the combination of velocities and positions of cluster member galaxies, along with data of the stellar velocity dispersion profile of the BCG, can impose constraints on the parameter space of the Chameleon model; for a cluster generated in GR, these constraints are at the same level as a joint lensing+kinematics analysis of a cluster modelled with a single mass profile, without the BCG data.