Photometric Redshifts and Stellar Masses for Galaxies from the DESI Legacy Imaging Surveys

Abstract

We present a catalog of photometric redshifts and stellar masses for galaxies from imaging surveys serving the Dark Energy Spectroscopic Instrument project. The imaging footprints cover an area of over 14,000 deg². This catalog contains about 0.17 billion morphologically classified galaxies with r < 23 mag. It covers the redshift range of z < 1 and the mass range of 8.4< {log}({M}_* )< 11.9. A total of five photometric bands are used, including three optical filters (g, r, and z) and two infrared filters (Wide-field Infrared Survey Explorer W1 and W2). We use k-nearest neighbors and local linear regression algorithms to estimate photometric redshifts. Based on a spectroscopic sample of about 2.2 million galaxies, we achieve a redshift bias of \overline{{{Δ }}{z}_norm}} = 2.4 × 10^-4, accuracy of {σ }_{{Δ }{z}_norm}} = 0.017, and outlier rate of about 5.1%. The stellar mass and other physical parameters are derived by stellar population synthesis model fitting based on our photometric redshifts. The differences in {log}({M}_* ) derived using spectroscopic and photometric redshifts present a 1σ dispersion of 0.09 dex.