A Merged Catalog of Clusters of Galaxies from Early Sloan Digital Sky Survey Data

We present a catalog of 799 clusters of galaxies in the redshift range z_est= 0.05 - 0.3 selected from ~400 deg^2 of early SDSS commissioning data alongthe celestial equator. The catalog is based on merging two independentselection methods -- a color-magnitude red-sequence maxBCG technique (B), and aHybrid Matched-Filter method (H). The BH catalog includes clusters withrichness \Lambda >= 40 (Matched-Filter) and N_gal >= 13 (maxBCG), correspondingto typical velocity dispersion of \sigma_v >~ 400 km s^{-1} and mass (within0.6 h^{-1) Mpc radius) >~ 5*10^{13} h^{-1} M_sun. This threshold is below Abellrichness class 0 clusters. The average space density of these clusters is2*10^{-5} h^3 Mpc^{-3}. All NORAS X-ray clusters and 53 of the 58 Abellclusters in the survey region are detected in the catalog; the 5 additionalAbell clusters are detected below the BH catalog cuts. The cluster richnessfunction is determined and found to exhibit a steeply decreasing clusterabundance with increasing richness. We derive observational scaling relationsbetween cluster richness and observed cluster luminosity and cluster velocitydispersion; these scaling relations provide important physical calibrations forthe clusters. The catalog can be used for studies of individual clusters, forcomparisons with other sources such as X-ray clusters and AGNs, and, withproper correction for the relevant selection functions, also for statisticalanalyses of clusters.