Probing Vainsthein-screening gravity with galaxy clusters using internal kinematics and strong and weak lensing

TL;DR

This study combines galaxy cluster lensing and kinematic data to test modified gravity theories, providing new constraints on Vainsthein-screening deviations and revealing potential tensions with general relativity.

Contribution

It introduces a novel combined analysis method using lensing and galaxy kinematics to constrain DHOST gravity theories, improving bounds on the coupling parameter Y_2.

Findings

New constraints on Y_2 parameter with about twofold improvement.

Detection of >2σ tension with General Relativity in one cluster.

Analysis of systematics affecting the combined kinematics and lensing approach.

Abstract

We use high-precision combined strong/weak lensing and kinematics measurements of the total mass profiles of the observed galaxy clusters MACS~J1206.2-0847 and Abell~S1063, to constrain the relativistic sector of the general DHOST dark energy theories, which exhibit a partial breaking of the so called Vainsthein screening mechanism, on the linear level of scalar fluctuations around a cosmological background. In particular, by using the \textsc{MG-MAMMPOSSt} framework developed in Pizzuti et al. 2021, for the kinematics analysis of member galaxies in clusters along with lensing mass profile reconstructions, we provide new constraints on the coupling $Y_2$ which governs the theory's relativistic contribution to the lensing potential. The new bound from the combination of kinematics and lensing measurements of MACS 1206, $Y_2=-0.12^{+0.66}_{-0.67}$ at $2\sigma$, provides about a 2-fold improvement on previous constraints. In the case of Abell~S1063 a $>2\sigma$ tension with the GR expectation arises. We discuss this in some detail, and we investigate the possible sources of systematics which can explain the tension. We further discuss why the combination of kinematics of member galaxies with lensing is capable of providing much tighter bounds compared to kinematics or lensing alone, and we explain how the number density profile of tracers, as well as the choice of the velocity anisotropy profile affects the final results.