THE SLOAN DIGITAL SKY SURVEY CO-ADD: A GALAXY PHOTOMETRIC REDSHIFT CATALOG

We present and describe a catalog of galaxy photometric redshifts (photo-z) for the Sloan Digital Sky Survey (SDSS) Co-add Data. We use the artificial neural network (ANN) technique to calculate the photo-z and the nearest neighbor error method to estimate photo-z errors for similar to 13 million objects classified as galaxies in the co-add with r < 24.5. The photo-z and photo-z error estimators are trained and validated on a sample of similar to 83,000 galaxies that have SDSS photometry and spectroscopic redshifts measured by the SDSS Data Release 7 (DR7), the Canadian Network for Observational Cosmology Field Galaxy Survey, the Deep Extragalactic Evolutionary Probe Data Release 3, the VIsible imaging Multi-Object Spectrograph-Very Large Telescope Deep Survey, and the WiggleZ Dark Energy Survey. For the best ANN methods we have tried, we find that 68% of the galaxies in the validation set have a photo-z error smaller than sigma(68) = 0.031. After presenting our results and quality tests, we provide a short guide for users accessing the public data.

Alfred P. Sloan Foundation

National Science Foundation

U.S. Department of Energy

National Aeronautics and Space Administration

Japanese Monbukagakusho

Max Planck Society

Higher Education Funding Council for England

American Museum of Natural History

Astrophysical Institute Potsdam

University of Basel

University of Cambridge

Case Western Reserve University

University of Chicago

Drexel University

Fermilab

Institute for Advanced Study

Japan Participation Group

Johns Hopkins University

Joint Institute for Nuclear Astrophysics

Kavli Institute for Particle Astrophysics and Cosmology

Korean Scientist Group

Chinese Academy of Sciences (LAMOST)

Los Alamos National Laboratory

Max-Planck-Institute for Astronomy (MPIA)

Max-Planck-Institute for Astrophysics (MPA)

New Mexico State University

Ohio State University

University of Pittsburgh

University of Portsmouth

Princeton University

United States Naval Observatory

University of Washington