The Voronoi Tessellation cluster finder in 2+1 dimensions

TL;DR

This paper introduces an improved Voronoi Tessellation cluster finder algorithm in 2+1 dimensions, capable of reliably detecting galaxy clusters up to redshift 1 and down to $10^{13.5}$ solar masses, using mock catalogs for validation.

Contribution

The paper presents a self-consistent Voronoi Tessellation cluster finder that does not assume astrophysical properties and demonstrates high completeness and purity in mock data.

Findings

Achieves >80% completeness and purity up to redshift 1.

Detects clusters down to $10^{13.5}$ solar masses.

Validated on mock catalogs consistent with $ m extit{ extbf{ extbf{Lambda}}}$CDM cosmology.

Abstract

We present a detailed description of the Voronoi Tessellation (VT) cluster finder algorithm in 2+1 dimensions, which improves on past implementations of this technique. The need for cluster finder algorithms able to produce reliable cluster catalogs up to redshift 1 or beyond and down to $10^{13.5}$ solar masses is paramount especially in light of upcoming surveys aiming at cosmological constraints from galaxy cluster number counts. We build the VT in photometric redshift shells and use the two-point correlation function of the galaxies in the field to both determine the density threshold for detection of cluster candidates and to establish their significance. This allows us to detect clusters in a self consistent way without any assumptions about their astrophysical properties. We apply the VT to mock catalogs which extend to redshift 1.4 reproducing the $\Lambda$CDM cosmology and the clustering properties observed in the SDSS data. An objective estimate of the cluster selection function in terms of the completeness and purity as a function of mass and redshift is as important as having a reliable cluster finder. We measure these quantities by matching the VT cluster catalog with the mock truth table. We show that the VT can produce a cluster catalog with completeness and purity $>80%$ for the redshift range up to $\sim 1$ and mass range down to $\sim 10^{13.5}$ solar masses.