The Northern Sky Optical Cluster Survey III: A Cluster Catalog Covering Pi Steradians

TL;DR

This paper presents a comprehensive catalog of over 15,000 galaxy clusters from the Northern Sky Optical Cluster Survey covering 11,411 square degrees, including improved measurements and comparisons with X-ray data and other catalogs.

Contribution

The study provides an updated, homogeneous galaxy cluster catalog with enhanced photometric redshifts, richness, luminosities, and substructure measures, covering both Northern and Southern Galactic Caps.

Findings

Over 15,000 candidate clusters identified.

Strong correlation between optical and X-ray luminosities.

Homogeneity confirmed across different survey regions.

Abstract

We present the complete galaxy cluster catalog from the Northern Sky Optical Cluster Survey, a new, objectively defined catalog of candidate galaxy clusters at z<0.25 drawn from the Digitized Second Palomar Observatory Sky Survey (DPOSS). The data presented here cover the Southern Galactic Cap, as well as the less-well calibrated regions of the Northern Galactic Cap. In addition, due to improvements in our cluster finder and measurement methods, we provide an updated catalog for the well-calibrated Northern Galactic Cap region previously published in Paper II. The complete survey covers 11,411 square degrees, with over 15,000 candidate clusters. We discuss improved photometric redshifts, richnesses and optical luminosities which are provided for each cluster. A variety of substructure measures are computed for a subset of over 11,000 clusters. We also discuss the derivation of dynamical radii r_200 and its relation to cluster richness. A number of consistency checks between the three areas of the survey are also presented, demonstrating the homogeneity of the catalog over disjoint sky areas. We perform extensive comparisons to existing optically and X-ray selected cluster catalogs, and derive new X-ray luminosities and temperatures for a subset of our clusters. We find that the optical and X-ray luminosities are well correlated, even using relatively shallow ROSAT All Sky Survey and DPOSS data. This survey provides a good comparison sample to the MaxBCG catalog based on Sloan Digital Sky Survey Data, and complements that survey at low redshifts 0.07<z<0.1.