Cluster formation and the Sunyaev-Zel'dovich power spectrum in modified gravity: the case of a phenomenologically extended DGP model

TL;DR

This paper explores how a phenomenologically extended DGP modified gravity model affects galaxy cluster formation and the Sunyaev-Zel'dovich power spectrum, providing observational constraints based on CMB data.

Contribution

It introduces a two-parameter extension of the DGP model and analyzes its impact on structure formation and SZ spectrum, offering new insights into deviations from Lambda-CDM.

Findings

Growth function is enhanced in the normal branch

SZ power spectrum is amplified compared to Lambda-CDM

Constraints on model parameters are derived from CMB data

Abstract

We investigate the effect of modified gravity on cluster abundance and the Sunyaev-Zel'dovich angular power spectrum. Our modified gravity is based on a phenomenological extension of the Dvali-Gabadadze-Porrati model which includes two free parameters characterizing deviation from Lambda-CDM cosmology. Assuming that Birkhoff's theorem gives a reasonable approximation, we study the spherical collapse model of structure formation and show that while the growth function changes to some extent, modified gravity gives rise to no significant change in the linear density contrast at collapse time. The growth function is enhanced in the so called normal branch, while in the "self-accelerating" branch it is suppressed. The Sunyaev-Zel'dovich angular power spectrum is computed in the normal branch, which turns out to be amplified compared to the Lambda-CDM case. This allows us to put observational constraints on the parameters of the modified gravity model using small scale CMB observation data.