Nonlinear evolution of initially biased tracers in modified gravity

TL;DR

This paper extends perturbation theory for modified gravity, enabling the analysis of biased tracers and their clustering statistics across various cosmological models, with practical computational tools provided.

Contribution

It develops a generalized formalism for biased tracers in modified gravity and connects Lagrangian and Standard Perturbation Theory kernels, including a public code.

Findings

Bias parameters are generally smaller in MG than in GR.

The formalism applies to multiple cosmological models like $f(R)$ and DGP.

Correlation functions and power spectra are computed for different MG models.

Abstract

In this work we extend the perturbation theory for modified gravity (MG) in two main aspects. First, the construction of matter overdensities from Lagrangian displacement fields is shown to hold in a general framework, allowing us to find Standard Perturbation Theory (SPT) kernels from known Lagrangian Perturbation Theory (LPT) kernels. We then develop a theory of biased tracers for generalized cosmologies, extending already existing formalisms for $\Lambda$CDM. We present the correlation function in Convolution-LPT and the power spectrum in SPT for $\Lambda$CDM, $f(R)$ Hu-Sawicky, and DGP braneworld models. Our formalism can be applied to many generalized cosmologies and to facilitate it, we are making public a code to compute these statistics. We further study the relaxation of bias with the use of a simple model and of excursion set theory, showing that in general the bias parameters have smaller values in MG than in General Relativity.