The SRG-eROSITA All-Sky Survey : Constraints on f(R) Gravity from Cluster Abundance

TL;DR

This paper uses the eROSITA all-sky survey cluster data combined with weak lensing measurements to place new constraints on f(R) gravity, finding no significant deviation from general relativity and highlighting the potential for future surveys to improve these limits.

Contribution

First constraints on f(R) gravity from cluster abundances alone, incorporating weak lensing calibration and neutrino mass effects, with tighter limits than previous studies.

Findings

No significant deviation from general relativity detected.

Upper limit of log |fR0| < -4.12 with neutrino mass considerations.

Constraints will improve with deeper future surveys.

Abstract

The evolution of the cluster mass function traces the growth of the linear density perturbations and can be utilized for constraining the parameters of cosmological and alternative gravity models. In this context, we present new constraints on potential deviations from general relativity by investigating the Hu-Sawicki parametrization of the f(R) gravity with the first SRG-eROSITA All-Sky Survey (eRASS1) cluster catalog in the Western Galactic Hemisphere in combination with the overlapping Dark Energy Survey Year 3, KiloDegree Survey and Hyper Supreme Camera data for weak lensing mass calibration. For the first time, we present constraints obtained from cluster abundances only. When we consider massless neutrinos, we find a strict upper limit of log |fR0| < -4.31 at 95% confidence level. Massive neutrinos suppress structure growth at small scales, and thus have the opposite effect of f(R) gravity. We consequently investigate the joint fit of the mass of the neutrinos with the modified gravity parameter. We obtain log |fR0| < -4.12 jointly with \sum m_\nu < 0.44 e.V. at 95% confidence level, tighter than the limits in the literature utilizing cluster counts only. At log |fR0|= - 6, the number of clusters is not significantly changed by the theory. Consequently, we do not find any statistical deviation from general relativity from the study of eRASS1 cluster abundance. Deeper surveys with eROSITA, increasing the number of detected clusters, will further improve constraints on log |fR0| and investigate alternative gravity theories.