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

Abstract

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 ≤ zest ≤ 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 Λcl ≥ 40 clusters in our survey lies in the range (1.6-1.8) × 10-5 h Mpc-3, ~1.5 times higher than the local distribution of comparably rich Abell richness class ≥0 clusters. The Λcl 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 Λcl 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.