Galaxy Clusters from the DESI Legacy Imaging Surveys. I. Cluster Detection

Based on the photometric redshift catalog of Zou et al., we apply a fast clustering algorithm to identify 540,432 galaxy clusters at z less than or similar to 1 in the DESI legacy imaging surveys, which cover a sky area of about 20,000 deg(2). Monte Carlo simulations indicate that the false-detection rate of our detecting method is about 3.1%. The total masses of galaxy clusters are derived using a calibrated richness-mass relation that is based on the observations of X-ray emission and the Sunyaev and Zel'dovich effect. The median redshift and mass of our detected clusters are about 0.53 and 1.23 x 10(14) M, respectively. Comparing with previous clusters identified using the data of the Sloan Digital Sky Survey; we can recognize most of them, especially those with high richness. Our catalog will be used for further statistical studies on galaxy clusters and environmental effects on galaxy evolution, etc.