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R. R. Gal, S. G. Djorgovski (Caltech), S. C. Odewahn (ASU), R. R. DeCarvalho (ON, Brazil), R. Brunner (Caltech)
The Northern Sky Optical Cluster Survey is a project to create an objective catalog of galaxy clusters over the entire high-galactic-latitude Northern sky. We use the object 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. This survey eliminates many of the subjective criteria of past surveys, and utilizes more information (especially colors) than the most similar recent survey, the APM (Dalton et al. 1992). This paper presents the details of our cluster detection technique, as well as some initial results for two small areas totaling ~60 square degrees. 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.
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The author(s) of this abstract have provided an email address for comments about the abstract: rrg@astro.caltech.edu