A comparison of algorithms for the construction of SZ cluster catalogues

Jean-Baptiste Melin ,D Yvon,M Betoule,P Carvalho,D L Harrison,J Delabrouille,J Bobin,J M Diego,M Le Jeune,P Mazzotta,M Hobson,D Herranz,N Aghanim,G Chon,J G Bartlett,Jean-Luc Starck ,G Rocha ,R Kneißl ,Jean-Claude Waizmann ,B Schaefer ,M López‐Caniego ,Matthias Bartelmann ,A Lasenby

doi:10.1051/0004-6361/201015689

Abstract

We evaluate the construction methodology of an all-sky catalogue of galaxy clusters detected through the Sunyaev-Zel'dovich (SZ) effect. We perform an extensive comparison of twelve algorithms applied to the same detailed simulations of the millimeter and submillimeter sky based on a Planck-like case. We present the results of this "SZ Challenge" in terms of catalogue completeness, purity, astrometric and photometric reconstruction. Our results provide a comparison of a representative sample of SZ detection algorithms and highlight important issues in their application. In our study case, we show that the exact expected number of clusters remains uncertain (about a thousand cluster candidates at |b|> 20 deg with 90% purity) and that it depends on the SZ model and on the detailed sky simulations, and on algorithmic implementation of the detection methods. We also estimate the astrometric precision of the cluster candidates which is found of the order of ~2 arcmins on average, and the photometric uncertainty of order ~30%, depending on flux.

Highlights

Galaxy cluster catalogues have played a long-standing, vital role in cosmology, providing important information on topics ranging from cosmological parameters to galaxy formation (Rosati et al 2002; Voit 2005)
We evaluated each extracted catalogue in terms of catalogue content and photometric recovery based on comparisons between the extracted catalogues and the simulated input SZ cluster catalogue
We compare different codes and algorithms to detect SZ galaxy clusters from multi-wavelength experiments using Plank’s instrumental characteristics. These methods may be usefully divided into direct methods using individual frequency maps, and indirect methods that first construct an SZ map in which they subsequently search for clusters

Summary

Introduction

Galaxy cluster catalogues have played a long-standing, vital role in cosmology, providing important information on topics ranging from cosmological parameters to galaxy formation (Rosati et al 2002; Voit 2005). The science potential of large cluster surveys is strong: They are, for instance, considered one of the central observational tools for illuminating the nature of dark energy (e.g., the Dark Energy Task Force Report Albrecht et al 2006, 2009). A suite of large cluster surveys planned over the coming years in the optical/IR, X-ray and millimeter bands will greatly extend the reach of cluster science by probing much larger volumes to higher redshifts with vastly superior statistics and control of systematics. Surveying the entire sky in 9 millimeter/submillimeter bands with ∼5–10 arcmin resolution over the channels most sensitive to the cosmic microwave background (CMB) anisotropies, the Planck satellite will find large numbers of clusters through the Sunyaev-Zel’dovich (SZ) effect (Sunyaev & Zeldovich 1970, 1972; Birkinshaw 1999; Carlstrom et al 2002). The Planck SZ catalogue will be the first

Methods

Results

Conclusion