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Published June 1, 2019 | Published + Accepted Version
Journal Article Open

The Complete Calibration of the Color-Redshift Relation (C3R2) Survey: Analysis and Data Release 2


The Complete Calibration of the Color-Redshift Relation (C3R2) survey is a multi-institution, multi-instrument survey that aims to map the empirical relation of galaxy color to redshift to i ~ 24.5 (AB), thereby providing a firm foundation for weak lensing cosmology with the Stage IV dark energy missions Euclid and WFIRST. Here we present 3171 new spectroscopic redshifts obtained in the 2016B and 2017A semesters with a combination of DEIMOS, LRIS, and MOSFIRE on the Keck telescopes. The observations come from all of the Keck partners: Caltech, NASA, the University of Hawaii, and the University of California. Combined with the 1283 redshifts published in DR1, the C3R2 survey has now obtained and published 4454 high-quality galaxy redshifts. We discuss updates to the survey design and provide a catalog of photometric and spectroscopic data. Initial tests of the calibration method performance are given, indicating that the sample, once completed and combined with extensive data collected by other spectroscopic surveys, should allow us to meet the cosmology requirements for Euclid, and make significant headway toward solving the problem for WFIRST. We use the full spectroscopic sample to demonstrate that galaxy brightness is weakly correlated with redshift once a galaxy is localized in the Euclid or WFIRST color space, with potentially important implications for the spectroscopy needed to calibrate redshifts for faint WFIRST and LSST sources.

Additional Information

© 2019 The American Astronomical Society. Received 2018 November 30; revised 2019 March 19; accepted 2019 April 3; published 2019 May 28. We thank the anonymous referee for a thorough and constructive report that improved this manuscript. The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. D.M., D.S., P.C., and J.R. acknowledge support by NASA ROSES grant 12-EUCLID12-0004. D.M. acknowledges support for this work from a NASA Postdoctoral Program Fellowship. This work was enabled by a NASA Keck grant.

Attached Files

Published - Masters_2019_ApJ_877_81.pdf

Accepted Version - 1904.06394.pdf


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August 19, 2023
October 20, 2023