Halos and Voids in f(R) Gravity

TL;DR

This study uses high-resolution simulations to analyze how f(R) gravity models affect the distribution of dark matter halos and voids, revealing increased numbers of massive halos and large voids, and proposing observational tests for these models.

Contribution

It demonstrates that the semi-analytic thin shell condition effectively describes screening in halos within f(R) gravity, and highlights the increased abundance of massive halos and voids as a testable prediction.

Findings

More massive halos and larger voids in f(R) models compared to DM.

Void halos are all unscreened, ideal for gravity tests.

Void counts are significantly higher in f(R) models, offering observational tests.

Abstract

In this paper, we study the distribution of dark matter halos and voids using high resolution simulations in f(R) gravity models with the chameleon mechanism to screen the fifth force in dense environment. For dark matter halos, we show that the semi-analytic thin shell condition, with a suitably-defined environment, provides a good approximation to describe the mass and environmental dependence of the screening of the fifth force in halos. Due to stronger gravity, there are far more massive halos and large voids in f(R) models compared with the \Lambda CDM model. The numbers of voids with an effective radius of 15Mpc/h are twice and four times as many as those in \Lambda CDM for f(R) models with |f_{R0}|=1e-5 and 1e-4 respectively. This provides a new means to test the models using the upcoming observational data. We also find that halos inside voids are all unscreened in our simulations, which are ideal objects for the gravity test.