December 3, 2015

Members of the COSMOS team were recently awarded Keck time (10 nights through NASA and 4 nights through Caltech) to begin a program designed to systematically measure the galaxy color-redshift relation, in preparation for the upcoming dark energy missions WFIRST and Euclid. The goal of this survey is to obtain a color-complete sample of high confidence redshifts, as described in Masters et al. 2015. Using a nonlinear dimensionality reduction (NLDR) technique known as the self-organizing map, Masters et al. were able to quantify the high-dimensional distribution of galaxy SEDs in COSMOS, enabling them to quantify where (in galaxy color space) high-confidence spectroscopy in the field currently exists, as well as where it is systematically missing. The under-sampled color regions are the primary focus of the survey, corresponding mostly to faint, star-forming galaxies at 0.2 < z < 2. A wealth of ancillary science will be possible with the resulting spectra, which will (by definition) probe populations of galaxies not studied previously. LRIS, DEIMOS, and MOSFIRE will be used for this program, which is anticipated to continue over the next several years.