The Northern Sky Optical Cluster Survey

Abstract

The Northern Sky Optical Cluster Survey aims to create an objective catalog of galaxy clusters over the entire high-galactic-latitude Northern sky. We use the catalogs generated from the Digitized Second Palomar Sky Survey (DPOSS, Djorgovski et al. 1999) as the basis for this survey. We apply a color criterion to select against field galaxies, and use a simple adaptive kernel technique to create galaxy density maps, combined with the bootstrap technique to make significance maps, from which density peaks are selected. We find a mean surface density of ∼1.5 clusters per square degree, consistent with the detection of richness class 0 and higher clusters to z∼0.3. In addition, we demonstrate an effective photometric redshift estimator for our clusters.