Fullshape power spectrum for the Symmetron modified gravity model

TL;DR

This paper develops a perturbation theory-based method to compute the fullshape galaxy power spectrum for the Symmetron modified gravity model, comparing it with the Hu-Sawicki model and validating it with mock data.

Contribution

It introduces a novel perturbation theory approach for the Symmetron model and demonstrates its effectiveness in modeling galaxy power spectra and redshift space distortions.

Findings

Symmetron growth rate similar to Hu-Sawicki F6 model within certain scales.

Proposed growth parametrization approximates both models with less than 0.6% deviation.

Validated the pipeline by recovering cosmological parameters from mock data.

Abstract

We make use of the perturbation theory for modified gravity models that we developed in previous works and apply it to construct the fullshape galaxy power spectrum for the Symmetron modified gravity model. First, we study the growth rate, that is a scale dependent quantity, and compare our results with those of the $n=1 $ Hu-Sawcki (HS) model, finding that the Symmetron has a growth quite similar to the HS F6 in the wavenumber interval $0.01 \leq k \leq 0.1 $ and for redshifts where Symmetron model is viable. We also propose a growth parametrization that turns to be a good approximation for the HS and Symmetron models, with a deviation less than $0.6 \%$. To compute the RSD multipoles we employ an expansion of the velocity moments generating function that is suitable for general modified gravity models. Later, we apply the fk-Perturbation Theory (fkPT) approximation to reduce the computation time of nonlinear kernels, to find the fullshape galaxy power spectrum for the Symmetron, and study the differences with HS model. The RSD multipoles of the Symmetron result similar to those of the HS F6 model. Next, we integrate this theory to an MCMC sampler and validate our results by fitting our parameters to EZMocks to recover the parameters that bring the model to GR. We found a similar agreement in the model validation between Symmetron and F6 model, recovering the simulation cosmological parameters, and concluding that our pipeline is ready to make cosmological parameters' inference with real data.