The rise of massive red galaxies: The color-magnitude and color-stellar mass diagrams for z _phot ≲ 2 from the multiwavelength survey by yale-chile

We present the color-magnitude and color-stellar mass diagrams for galaxies with z _phot ≲ 2, based on a K ^(AB) < 22 catalog of the × □^° Extended Chandra Deep Field South from the MUltiwavelength Survey by Yale-Chile. Our main sample of 7840 galaxies contains 1297 M _*>10¹¹ M _⊙ galaxies in the range 0.2 < z _phot < 1.8. We show empirically that this catalog is approximately complete for M _*>10¹¹ M _⊙ galaxies for z _phot < 1.8. For this mass-limited sample, we show that the locus of the red sequence color-stellar mass relation evolves as Δ(u - r) (-0.44 ± 0.02)z _phot for z _phot ≲ 1.2. For z _phot ≳ 1.3, however, we are no longer able to reliably distinguish red and blue subpopulations from the observed color distribution; we show that this would require much deeper near-infrared data. At 1.5 < z _phot < 1.8, the comoving number density of M _*>10¹¹ M _⊙ galaxies is 50% of the local value, with a red fraction of 33%. Making a parametric fit to the observed evolution, we find n _tot(z) (1 + z _phot)^{-0.520.12(0.20)}. We find stronger evolution in the red fraction: f _red(z) (1 + z _phot) ^{-1.170.18(0.21)}. Through a series of sensitivity analyses, we show that the most important sources of systematic error are (1) systematic differences in the analysis of the z ≈ 0 and z ≫ 0 samples; (2) systematic effects associated with details of the photometric redshift calculation; and (3) uncertainties in the photometric calibration. With this in mind, we show that our results based on photometric redshifts are consistent with a completely independent analysis which does not require redshift information for individual galaxies. Our results suggest that, at most, 1/5 of local red sequence galaxies with M _*>10¹¹ M _⊙ were already in place at z 2.