The Santiago-Harvard-Edinburgh-Durham void comparison II: unveiling the Vainshtein screening using weak lensing

TL;DR

This study investigates cosmic voids in modified gravity models, especially nDGP, using simulations and weak lensing profiles to identify potential observational signatures that distinguish these models from standard cosmology.

Contribution

It provides the first detailed analysis of void lensing signatures in nDGP models, comparing different void identification methods and screening mechanisms.

Findings

Void profiles in nDGP are more under-dense than in ΛCDM.

Weak lensing signals around voids differ significantly between models.

2D voids show stronger differences in lensing signals, aiding model discrimination.

Abstract

We study cosmic voids in the normal-branch Dvali-Gabadadze-Porrati (nDGP) braneworld models, which are representative of a class of modified gravity theories where deviations from General Relativity are usually hidden by the Vainshtein screening in high-density environments. This screening is less efficient away from these environments, which makes voids ideally suited for testing this class of models. We use N-body simulations of $\Lambda$-cold dark matter ($\Lambda$CDM) and nGDP universes, where dark matter haloes are populated with mock galaxies that mimic the clustering and number densities of the BOSS CMASS galaxy sample. We measure the force, density and weak lensing profiles around voids identified with six different algorithms. Compared to $\Lambda$CDM, voids in nDGP are more under-dense due to the action of the fifth force that arises in these models, which leads to a faster evacuation of matter from voids. This leaves an imprint on the weak lensing tangential shear profile around nDGP voids, an effect that is particularly strong for 2D underdensities that are identified in the plane-of-the-sky. We make predictions for the feasibility of distinguishing between nDGP and $\Lambda$CDM using void lensing in upcoming large-scale surveys such as LSST and Euclid. We compare with the analysis of voids in chameleon gravity theories and find that the weak lensing signal for 3D voids is similar to nDGP, whereas for 2D voids the differences with $\Lambda$CDM are much stronger for the chameleon gravity case, a direct consequence of the different screening mechanisms operating in these theories.