Cluster-counterpart Voids: Void Identification from Galaxy Density Field

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 a 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 × 10 ^14 h ^−1 M _⊙ from a galaxy sample with the mean number density, $\bar{n}=4.4\times {10}^{-3}{({h}^{-1}\,\mathrm{Mpc})}^{-3}$ . When the mean density is increased to $\bar{n}={10}^{-2}{({h}^{-1}\,\mathrm{Mpc})}^{-3}$ , the detection rate is enhanced by ∼2%–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.

Keywords

• Large-scale structure of the universe
• Voids