Weak lensing peak count as a probe of f(R) theories

TL;DR

This paper explores how weak lensing peak counts can serve as a powerful tool to differentiate between General Relativity and $f(R)$ modified gravity theories, providing forecasts for future survey constraints.

Contribution

It introduces a novel application of peak statistics to constrain $f(R)$ theories and forecasts their effectiveness with Euclid-like survey data.

Findings

Peak statistics can distinguish between GR and $f(R)$ models.

Strong constraints on $f(R)$ parameters are achievable.

Further analysis needed for redshift selection effects.

Abstract

Weak gravitational lensing by galaxy clusters on faint higher redshift galaxies has been traditionally used to study the cluster mass distribution and as a tool to identify clusters as peaks in the shear maps. However, it becomes soon clear that peaks statistics can also be used as a way to constrain the underlying cosmological model due to its dependence on both the cosmic expansion rate and the growth rate of structures. This feature makes peak statistics particularly interesting from the point of view of discriminating between General Relativity and modified gravity. Here we consider a general class of $f(R)$ theories and compute the observable mass function based on the aperture mass statistics. We complement our theoretical analysis with a Fisher matrix forecast of the constraints that an Euclid\,-\,like survey can impose on the $f(R)$ model parameters. We show that peak statistics alone can in principle discriminate between General Relativity and $f(R)$ models and strongly constrain the $f(R)$ parameters that are sensitive to the non-linear growth of structure. However, further analysis is needed in order to include possible selection function in the peaks redshift determination.