# The Voronoi Tessellation cluster finder in 2+1 dimensions

Soares-Santos, M; de Carvalho, R R; Annis, J; Gal, R R; La Barbera, F; Lopes, P A A; Wechsler, R H; Busha, M T; Gerke, B F (2010). The Voronoi Tessellation cluster finder in 2+1 dimensions. Astrophysical Journal, 727(1):45.

## 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.

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.

## Citations

26 citations in Web of Science®
6 citations in Scopus®

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Item Type: Journal Article, refereed, original work 07 Faculty of Science > Institute for Computational Science 530 Physics English 2010 23 Feb 2012 22:07 05 Apr 2016 15:40 Institute of Physics Publishing 0004-637X https://doi.org/10.1088/0004-637X/727/1/45 http://arxiv.org/abs/1011.3458
Permanent URL: https://doi.org/10.5167/uzh-60056

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