The KPNO/Deeprange Distant Cluster Survey. I. The Catalog and the Space Density of Intermediate-Redshift Clusters

We have conducted an automated search for galaxy clusters within a contiguous 16 deg² I-band survey in the north Galactic hemisphere. A matched filter detection algorithm identifies 444 cluster candidates in the range 0.2<~z<~1.2. The full catalog is presented along with the results from a follow-up spectroscopic survey. The estimated redshift distribution of the cluster candidates is consistent with a constant comoving density over the range 0.2<=z_est<=0.8. A decline in the cluster space density by more than a factor of 3 over this redshift range is rejected at the greater than 99.9% confidence level. We find that the space density of Λ_cl>=40 clusters in our survey lies in the range (1.6-1.8)×10^-5 h³₇₅ Mpc^-3, ~1.5 times higher than the local distribution of comparably rich Abell richness class >=0 clusters. The Λ_cl distribution is consistent with a power law. The discrepancy between the space density of Abell clusters and the clusters in this survey declines quickly as Λ_cl increases, suggesting that the difference at lower richness is due to significant incompleteness in the Abell catalog. A percolation analysis reveals that 10%-20% of the spectroscopically confirmed distant clusters are linked into superclusters at overdensities between 10<δρ/ρ<50, similar to what is seen in the local cluster distribution. This suggests that there has been little evolution of the cluster-cluster correlation length for z<~0.5.