Modelling Void Abundance in Modified Gravity

TL;DR

This paper develops a theoretical model for predicting cosmic void abundance in various gravity theories, validates it with simulations, and explores its potential for constraining modified gravity using upcoming galaxy survey data.

Contribution

It introduces an extended excursion set formalism with drifting diffusive barriers for void prediction in modified gravity, improving upon previous static barrier models.

Findings

Model accurately predicts dark matter and galaxy void abundances.

Void counts can constrain modified gravity parameters.

Galaxy voids pose challenges for gravity constraints.

Abstract

We use a spherical model and an extended excursion set formalism with drifting diffusive barriers to predict the abundance of cosmic voids in the context of general relativity as well as f(R) and symmetron models of modified gravity. We detect spherical voids from a suite of N-body simulations of these gravity theories and compare the measured void abundance to theory predictions. We find that our model correctly describes the abundance of both dark matter and galaxy voids, providing a better fit than previous proposals in the literature based on static barriers. We use the simulation abundance results to fit for the abundance model free parameters as a function of modified gravity parameters, and show that counts of dark matter voids can provide interesting constraints on modified gravity. For galaxy voids, more closely related to optical observations, we find that constraining modified gravity from void abundance alone may be significantly more challenging. In the context of current and upcoming galaxy surveys, the combination of void and halo statistics including their abundances, profiles and correlations should be effective in distinguishing modified gravity models that display different screening mechanisms.