Weak lensing by galaxy troughs with modified gravity

TL;DR

This study investigates how modified gravity theories influence gravitational lensing signals around galaxy regions with different densities, using simulations to compare predictions with standard cosmology.

Contribution

It introduces a detailed analysis of lensing signals in modified gravity models, highlighting scale-independent effects on underdense and overdense lines of sight.

Findings

Modified gravity models enhance lensing signals compared to $\ m BCDM$.

The effect size is consistent across underdense and overdense regions.

Results are robust against variations in halo mass, redshift, and line of sight criteria.

Abstract

We study the imprints that theories of gravity beyond GR can leave on the lensing signal around line of sight directions that are predominantly halo-underdense (called troughs) and halo-overdense. To carry out our investigations, we consider the normal branch of DGP gravity, as well as a phenomenological variant thereof that directly modifies the lensing potential. The predictions of these models are obtained with N-body simulation and ray-tracing methods using the ECOSMOG and Ray-Ramses codes. We analyse the stacked lensing convergence profiles around the underdense and overdense lines of sight, which exhibit, respectively, a suppression and a boost w.r.t. the mean in the field of view. The modifications to gravity in these models strengthen the signal w.r.t. $\Lambda{\rm CDM}$ in a scale-independent way. We find that the size of this effect is the same for both underdense and overdense lines of sight, which implies that the density field along the overdense directions on the sky is not sufficiently evolved to trigger the suppression effects of the screening mechanism. These results are robust to variations in the minimum halo mass and redshift ranges used to identify the lines of sight, as well as to different line of sight aperture sizes and criteria for their underdensity and overdensity thresholds.