Cluster-counterpart Voids: Void Identification from Galaxy Density Field

TL;DR

This paper extends a void-identification method to galaxy density fields, enabling the detection of cosmic voids corresponding to galaxy clusters with high reliability, useful for analyzing galaxy survey data.

Contribution

The authors adapt a void-cluster correspondence method for galaxy density fields, optimizing parameters for practical application in galaxy surveys.

Findings

Achieved 60-67% completeness and reliability for voids above 3x10^{14}h^{-1}M_{} from galaxy data.

Detection rate improves by 2-7% with higher galaxy density.

Method is insensitive to density weighting schemes.

Abstract

We identify cosmic voids from galaxy density fields under the theory of void-cluster correspondence. We extend the previous novel void-identification method developed for the matter density field to the galaxy density field for practical applications. From cosmological N-body simulations, we construct galaxy number- and mass-weighted density fields to identify cosmic voids that are counterparts of galaxy clusters of specific mass. The parameters for the cluster-counterpart void identification such as Gaussian smoothing scale, density threshold, and core volume fraction are found for galaxy density fields. We achieve about $60$--$67\%$ of completeness and reliability for identifying the voids of corresponding cluster mass above $3\times10^{14}h^{-1}M_{\odot}$ from a galaxy sample with the mean number density, $\bar{n}=4.4\times10^{-3} (h^{-1}{\rm Mpc})^{-3}$. When the mean density is increased to $\bar{n}=10^{-2} (h^{-1}{\rm Mpc})^{-3}$, the detection rate is enhanced by $\sim2$--$7\%$ depending on the `mass scale' of voids. We find that the detectability is insensitive to the density weighting scheme applied to generate the density field. Our result demonstrates that we can apply this method to the galaxy redshift survey data to identify cosmic voids corresponding statistically to the galaxy clusters in a given mass range.