An Automated Cluster Finder: The Adaptive Matched Filter

Abstract

We describe an automated method for detecting clusters of galaxies in imaging and redshift galaxy surveys. The adaptive matched Ðlter (AMF) method utilizes galaxy positions, magnitudes, andÈwhen availableÈphotometric or spectroscopic redshifts to Ðnd clusters and determine their redshift and richness. The AMF can be applied to most types of galaxy surveys, from two-dimensional (2D) imaging surveys, to multiband imaging surveys with photometric redshifts of any accuracy (2.5 dimensional to three-dimensional (3D) redshift surveys. The AMF can also be utilized in the selection of [21 2 D]), clusters in cosmological N-body simulations. The AMF identiÐes clusters by Ðnding the peaks in a cluster likelihood map generated by convolving a galaxy survey with a Ðlter based on a model of the cluster and Ðeld galaxy distributions. In tests on simulated 2D and data with a magnitude limit of 21 2 D r@ B 23.5, clusters are detected with an accuracy of *z B 0.02 in redshift and D10% in richness to z [ 0.5. Detecting clusters at higher redshifts is possible with deeper surveys. In this paper we present the theory behind the AMF and describe test results on synthetic galaxy catalogs.