The application of photometric redshifts to the SDSS early data release

The Early Data Release (EDR) from the Sloan Digital Sky Survey provides one of the largest multicolor photometric catalogs currently available to the astronomical community. In this paper we present the first application of photometric redshifts to the ∼6 million extended sources in these data (with 1.8 million sources having r′< 21). Utilizing a range of photometric redshift techniques, from empirical to template and hybrid techniques, we investigate the statistical and systematic uncertainties present in the redshift estimates for the EDR data. For r′< 21, we find that the redshift estimates provide realistic redshift histograms with an rms uncertainty in the photometric redshift relation of 0.035 at r′< 18 and rising to 0.1 at r′< 21. We conclude by describing how these photometric redshifts and derived quantities, such as spectral type, rest-frame colors, and absolute magnitudes, are stored in the SDSS database. We provide sample queries for searching on photometric redshifts and list the current caveats and issues that should be understood before using these photometric redshifts in statistical analyses of the SDSS galaxies.