The space density and colors of massive galaxies at 2 < z < 3: The predominance of distant red galaxies

Abstract

Using the deep multiwavelength MUSYC, GOODS, and FIRES surveys we construct a stellar mass-limited sample of galaxies at 2 ! z ! 3. The sample comprises 294 galaxies with M 1 1011 M distributed over four , independent fields with a total area of almost 400 arcmin2. The mean number density of massive galaxies in this redshift range 11 4 3 Mpc 3. We present median values and 25th and 75th r(M 1 10 M ) p (2.2 0.6)#10 h , 70 percentiles for the distributions of observed R magnitudes, observed J K colors, and rest-frame ultraviolet AB s continuum slopes, M/L ratios, and U V colors. The galaxies show a large range in all these properties. The V “median galaxy” is faint in the observer’s optical (R p 25.9), red in the observed near-IR (J K p 2.48), AB s has a rest-frame UV spectrum that is relatively flat in F (b p 0.4), and rest-frame optical colors resembling l those of nearby spiral galaxies (U V p 0.62). We determine which galaxies would be selected as Lyman break galaxies (LBGs) or distant red galaxies (DRGs, having J K 1 2.3) in this mass-limited sample. By number s DRGs make up 69% of the sample, and LBGs 20%, with a small amount of overlap. By mass DRGs make up 77%, and LBGs 17%. Neither technique provides a representative sample of massive galaxies at 2 ! z ! 3 as they only sample the extremes of the population. As we show here, multiwavelength surveys with high-quality photometry are essential for an unbiased census of massive galaxies in the early universe. The main uncertainty in this analysis is our reliance on photometric redshifts; confirmation of the results presented here requires extensive near-infrared spectroscopy of optically faint samples.