Validating estimates of the growth rate of structure with modified gravity simulations

TL;DR

This study validates a method for estimating the growth rate of cosmic structure in modified gravity models using galaxy clustering data, successfully applying it to mock and real data to constrain DGP gravity parameters.

Contribution

It demonstrates that the clustering wedges model accurately recovers growth rate differences in modified gravity simulations, enabling constraints on DGP gravity from observational data.

Findings

The model recovers the true growth rate difference in simulations.

It constrains the DGP cross-over scale to be greater than 3090 Mpc/h.

The method is effective even with significant enhancements in $f\sigma_8$.

Abstract

We perform a validation of estimates of the growth rate of structure, described by the parameter combination $f\sigma_8$, in modified gravity cosmologies. We consider an analysis pipeline based on the redshift-space distortion modelling of the clustering wedges statistic of the galaxy correlation function and apply it to mock catalogues of $\Lambda{\rm CDM}$ and the normal branch of DGP cosmologies. We employ a halo occupation distribution approach to construct our mocks, which we ensure resemble the CMASS sample from BOSS in terms of the total galaxy number density and large scale amplitude of the power spectrum monopole. We show that the clustering wedges model successfully recovers the true growth rate difference between DGP and $\Lambda{\rm CDM}$, even for cases with over 40\% enhancement in $f\sigma_8$ compared to $\Lambda{\rm CDM}$. The unbiased performance of the clustering wedges model allows us to use the growth rate values estimated from the BOSS DR12 data to constrain the cross-over scale $r_c$ of DGP gravity to $\left[r_cH_0\right]^{-1} < 0.97$ ($2\sigma$) or $r_c > 3090\ {\rm Mpc}/h$, cutting into the interesting region of parameter space with $r_c \sim H_0^{-1}$ using constraints from the growth of structure alone.