We present a catalog of 799 clusters of galaxies in the redshift range z _ { est } = 0.05 - 0.3 selected from \sim 400 deg ^ { 2 } of early SDSS commissioning data along the celestial equator .
The catalog is based on merging two independent selection methods – a color-magnitude red-sequence maxBCG technique ( B ) , and a Hybrid Matched-Filter method ( H ) .
The BH catalog includes clusters with richness \Lambda \geq 40 ( Matched-Filter ) and N _ { gal } \geq 13 ( maxBCG ) , corresponding to typical velocity dispersion of \sigma _ { v } \gtrsim 400 km s ^ { -1 } and mass ( within 0.6 h ^ { -1 } Mpc radius ) \gtrsim 5 \times 10 ^ { 13 } h ^ { -1 } M _ { \sun } .
This threshold is below Abell richness class 0 clusters .
The average space density of these clusters is 2 \times 10 ^ { -5 } h ^ { 3 } Mpc ^ { -3 } .
All NORAS X-ray clusters and 53 of the 58 Abell clusters in the survey region are detected in the catalog ; the 5 additional Abell clusters are detected below the BH catalog cuts .
The cluster richness function is determined and found to exhibit a steeply decreasing cluster abundance with increasing richness .
We derive observational scaling relations between cluster richness and observed cluster luminosity and cluster velocity dispersion ; these scaling relations provide important physical calibrations for the clusters .
The catalog can be used for studies of individual clusters , for comparisons with other sources such as X-ray clusters and AGNs , and , with proper correction for the relevant selection functions , also for statistical analyses of clusters .