# Cosmic voids uncovered -- first-order statistics of depressions in the biased density field

## TL;DR

This paper improves void size function models by redefining voids using a new algorithm, validating their applicability to biased tracers, and demonstrating their potential for cosmological studies.

## Contribution

It introduces a new void selection algorithm, validates the size function model on biased tracers, and links tracer bias to void properties for cosmological applications.

## Key findings

- The new algorithm redefines voids and conserves volume.
- The size function model is validated on biased tracers.
- A relation between tracer bias and void size is established.

## Abstract

Cosmic voids are the major volume component in the matter distribution of the Universe. They posses great potential for constraining dark energy as well as for testing theories of gravity. Nevertheless, in spite of their growing popularity as cosmological probes, a gap of knowledge between cosmic void observations and theory still persists. In particular, the void size function models proposed in literature have been proven unsuccessful in reproducing the results obtained from cosmological simulations in which cosmic voids are detected from biased tracers of the density field, undermining the possibility of using them as cosmological probes. The goal of this work is to cover this gap. In particular, we make use of the findings of a previous work in which we have improved the void selection procedure, presenting an algorithm that redefines the void ridges and, consequently, their radius. By applying this algorithm, we validate the volume conserving model of the void size function on a set of unbiased simulated density field tracers. We highlight the difference in the internal structure between voids selected in this way and those identified by the popular VIDE void finder. We also extend the validation of the model to the case of biased tracers. We find that a relation exists between the tracer used to sample the underlying dark matter density field and its unbiased counterpart. Moreover, we demonstrate that, as long as this relation is accounted for, the size function is a viable approach for studying cosmology with cosmic voids.