The High-Mass End of the Red Sequence at z~0.55 from SDSS-III/BOSS: completeness, bimodality and luminosity function

Abstract

We have developed an analytical method based on forward-modeling techniques to characterize the high-mass end of the red sequence (RS) galaxy population at redshift $z\sim 0.55$, from the DR10 BOSS CMASS spectroscopic sample, which comprises $\sim 600,000$ galaxies. The method, which follows an unbinned maximum likelihood approach, allows the deconvolution of the intrinsic CMASS colour-colour-magnitude distributions from photometric errors and selection effects. This procedure requires modeling the covariance matrix for the i-band magnitude, g-r colour and r-i colour using Stripe 82 multi-epoch data. Our results indicate that the error-deconvolved intrinsic RS distribution is consistent, within the photometric uncertainties, with a single point ($<0.05\mathrm{mag}$) in the colour-colour plane at fixed magnitude, for a narrow redshift slice. We have computed the high-mass end (${}^{0.55}{M}_i\lesssim -22$) of the ${}^{0.55}i$-band RS Luminosity Function (RS LF) in several redshift slices within the redshift range $0.52<z<0.63$. In this narrow redshift range, the evolution of the RS LF is consistent, within the uncertainties in the modeling, with a passively-evolving model with $\hat{I}{¦}_{\ast }=(7.248\pm 0.204)\times 10^{-4}$ Mpc${}^{-3}$ mag${}^{-1}$, fading at a rate of $1.5\pm 0.4$ mag per unit redshift. We report RS completeness as a function of magnitude and redshift in the CMASS sample, which will facilitate a variety of galaxy-evolution and clustering studies using BOSS. Our forward-modeling method lays the foundations for future studies using other dark-energy surveys like eBOSS or DESI, which are affected by the same type of photometric blurring/selection effects.

27 pages, 20 figures, accepted for publication in MNRAS