Lognormal Distribution of Cosmic Voids in Simulations and Mocks

TL;DR

This study confirms that the void size distribution in cosmic simulations and mocks follows a 3-parameter log-normal distribution and explores how environmental factors influence its shape parameters and the emergence of a second population.

Contribution

It demonstrates the universality of the 3-parameter log-normal distribution for cosmic voids across different environments and establishes quantitative relations between distribution shape and environmental metrics.

Findings

Void size distributions follow a 3-parameter log-normal distribution.

Environmental effects significantly influence the distribution's shape parameters.

Presence of a second population correlates with a threshold of 3.84% nonzero central density voids.

Abstract

Following up on previous studies, we here complete a full analysis of the void size distributions of the Cosmic Void Catalog (CVC) based on three different simulation and mock catalogs; dark matter, haloes and galaxies. Based on this analysis, we attempt to answer two questions: Is a 3-parameter log-normal distribution a good candidate to satisfy the void size distributions obtained from different types of environments? Is there a direct relation between the shape parameters of the void size distribution and the environmental effects? In an attempt to answer these questions, we here find that all void size distributions of these data samples satisfy the 3-parameter log-normal distribution whether the environment is dominated by dark matter, haloes or galaxies. In addition, the shape parameters of the 3-parameter log-normal void size distribution seem highly affected by environment, particularly existing substructures. Therefore, we show two quantitative relations given by linear equations between the skewness and the maximum tree depth, and variance of the void size distribution and the maximum tree depth directly from the simulated data. In addition to this, we find that the percentage of the voids with nonzero central density in the data sets has a critical importance. If the number of voids with nonzero central densities reaches greater and or equal to 3.84 percentage in a simulation/mock sample, then a second population is observed in the void size distributions. This second population emerges as a second peak in the log-normal void size distribution at larger radius.