2004MNRAS.353...30C

We have analysed five-epoch Great Observatories Origins Deep Survey (GOODS) HST-ACS B, V, I₇₇₅and z data sets (v. 1.0 release), in conjunction with existing VLT-ISAAC imaging in the J, H and K_s bands, to derive estimated redshifts for the sample of 198 extremely red galaxies (ERGs) with K_s < 22 (Vega) and (I₇₇₅-K_s) > 3.92 selected by (Roche, Dunlop & Almaini (2003)) from 50.4 arcmin² of the GOODS/Chandra Deep Field South. We find that, at this depth, the ERG population spans the redshift range 0.5 < z_phot< 4.75 and over two decades in mass (∼3x10⁹ M_☉ to ∼3x10¹¹ M_☉). Our results show that the dust-corrected red envelope of galaxy evolution is well modelled by a starburst at redshift z_f= 5 followed thereafter by passive evolution. We explore the evolution of the ERG luminosity function (LF) from redshifts <z_phot≥ 1.0 to <z_phot≥ 2.5 and compare it with the global K_s-band LF at redshifts 1 < z_phot< 2. We find that the bright end of the ERG LF does not decrease from redshifts <z_phot≥ 2.0 to <z_phot≥ 2.5 and we connect this fact with the presence of progenitors of the local L > L* population at redshifts z_phot> 2. We determine lower limits of ρ_c= (6.1±1.9)x10^–5/Mpc3 and ρ_c_= (2.1±1.1)x10^–5/Mpc3 on the comoving densities of progenitors of local massive galaxies already assembled at redshifts <z_phot≥ 2.5 and <z_phot≥ 3.5, respectively. We have investigated the existence of high-redshift Lyman-break galaxies massive enough to be included in this ERG sample. Out of an initial list of 12 potential very high redshift candidates, we have identified two ERGs which have a high probability of lying at z_phot> 4. We discuss the advantages of multicolour to single-colour selection techniques in obtaining reliable lists of very high redshift candidate sources, and present revised lower redshift estimates for sources previously claimed as potential z > 5 dropouts in recent studies.