Detecting Clusters of Galaxies in SDSS : I . Photometric Redshifts of Galaxies

With the great volume of data of Sloan Digital Sky Survey (SDSS) being released, large area and complete galaxy cluster survey becomes available. As the first step of our cluster study, we present a study of photometric redshifts (PRs) of galaxies using five-band photometry obtained by SDSS. The comprehensive application of several empirical methods, such as template fitting, color-magnituderedshift relation and quadratic correction, improves PR estimation significantly. In a test of about 460,000 galaxies with known spectroscopic redshifts (SRs), our method achieves a better result, namely that the PR uncertainty can be reduced to σPR ∼ 0.022. The application to SDSS photometric data suggests that with the available Sloan spectroscopic sample this method is practical and effective to a limiting magnitude of r′ ∼ 21. Subject headings: galaxies: clusters — galaxies: distances and redshifts — methods: data analysis