Testing gravity with halo density profiles observed through gravitational lensing

TL;DR

This paper proposes a new method to test modified gravity theories with the Vainshtein mechanism by analyzing galaxy cluster density profiles through gravitational lensing, comparing predictions with observations to constrain model parameters.

Contribution

It introduces a novel observational test of the Vainshtein screening mechanism using gravitational lensing data of galaxy clusters, focusing on the transition effects on surface mass density.

Findings

Constraints on the transition scale of the Vainshtein mechanism.

Comparison of theoretical profiles with observed lensing data.

Limits on the amplitude of scalar field contributions.

Abstract

We present a new test of the modified gravity endowed with the Vainshtein mechanism with the density profile of a galaxy cluster halo observed through gravitational lensing. A scalar degree of freedom in the galileon modified gravity is screened by the Vainshtein mechanism to recover Newtonian gravity in high-density regions, however it might not be completely hidden on the outer side of a cluster of galaxies. Then the modified gravity might yield an observational signature in a surface mass density of a cluster of galaxies measured through gravitational lensing, since the scalar field could contribute to the lensing potential. We investigate how the transition in the Vainshtein mechanism affects the surface mass density observed through gravitational lensing, assuming that the density profile of a cluster of galaxies follows the original Navarro-Frenk-White (NFW) profile, the generalized NFW profile and the Einasto profile. We compare the theoretical predictions with observational results of the surface mass density reported recently by other researchers. We obtain constraints on the amplitude and the typical scale of the transition in the Vainshtein mechanism in a subclass of the generalized galileon model.