Constraints on Modified Gravity from Sunyaev-Zeldovich Cluster Surveys

TL;DR

This paper assesses how current and future Sunyaev-Zeldovich cluster surveys can constrain f(R) gravity models, showing significant improvements over existing limits by analyzing cluster counts and power spectra.

Contribution

It provides a detailed forecast of constraints on f(R) gravity from SZ cluster surveys, incorporating effects on mass function, bias, and power spectrum, and demonstrates the added value of combining observables.

Findings

Planck survey can reduce current f(R) constraints by a factor of four.

Cluster power spectrum improves constraints beyond number counts alone.

Combining counts and power spectrum breaks degeneracies with dark energy parameters.

Abstract

We investigate the constraining power of current and future Sunyaev-Zeldovich cluster surveys on the f(R) gravity model. We use a Fisher matrix approach, adopt self-calibration for the mass- observable scaling relation, and evaluate constraints for the SPT, Planck, SPTPol and ACTPol surveys. The modified gravity effects on the mass function, halo bias, matter power spectrum, and mass-observable relation are taken into account. We show that, relying on number counts only, the Planck cluster catalog is expected to reduce current upper limits by about a factor of four, to {\sigma}fR0 = 3 {\times} 10-5 (68% confidence level). Adding the cluster power spectrum further improves the constraints to {\sigma}fR0 = 10-5 for SPT and Planck, and {\sigma}fR0 = 3 {\times} 10-6 for SPTPol, pushing cluster constraints significantly beyond the limit where number counts have no constraining power due to the chameleon screening mechanism. Further, the combination of both observables breaks degeneracies, especially with the expansion history (effective dark energy density and equation of state). The constraints are only mildly worsened by the use of self-calibration but depend strongly on the mass threshold of the cluster samples.