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A New Method For Galaxy Cluster Detection. I. The Algorithm

2000/04/30 by Michael D. Gladders, H. K. C. Yee · 67 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Scientific Research and Discoveries #astro-ph

paper · pdf · doi:10.1086/301557

published as Astron.J.120:2148,2000 · To appear in November AJ, 22 pages, including 10 embedded figures, two-column preprint using aas2pp4 style file. For information on the associated 100 square degree, z~1 cluster survey, see http://www.astro.utoronto.ca/~gladders/RCS/

arxiv created 2000/08/05 · openalex publication_date 2000/10/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31

Abstract

Numerous methods for finding clusters at moderate to high redshifts have been proposed in recent years, at wavelengths ranging from radio to X-rays. In this paper we describe a new method for detecting clusters in two-band optical/near-IR imaging data. The method relies upon the observation that all rich clusters, at all redshifts observed so far, appear to have a red sequence of early-type galaxies. The emerging picture is that all rich clusters contain a core population of passively evolving elliptical galaxies that are coeval and formed at high redshifts. The proposed search method exploits this strong empirical fact by using the red sequence as a direct indicator of overdensity. The fundamental advantage of this approach is that with appropriate filters, cluster elliptical galaxies at a given redshift are redder than all normal galaxies at lower redshifts. A simple color cut thus virtually eliminates all foreground contamination, even at significant redshifts. In this paper, one of a series of two, we describe the underlying assumptions and basic techniques of the method in detail and contrast the method with those used by other authors. We provide a brief demonstration of the effectiveness of the technique using a real photometric sample with redshift data, and from this we conclude that the method offers a powerful yet simple way of identify galaxy clusters. We find that the method can reliably detect structures to masses as small as groups with velocity dispersions of only ∼300 km s -1 , with redshifts for all detected structures estimated to an accuracy of ∼10%.

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