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 deg 2 . 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 . 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 W 1 and W 2). 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  = 2.4 × 10 −4 , accuracy of  = 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 derived using spectroscopic and photometric redshifts present a 1 σ dispersion of 0.09 dex.