Confronting theoretical models with the observed evolution of the galaxy population out to z 4

We construct light cones for the semi-analytic galaxy formation simulation of Guo et al. and make mock catalogues for comparison with deep high-redshift surveys. Photometric properties are calculated with two different stellar population synthesis codes in order to study sensitivity to this aspect of the modelling. The catalogues are publicly available and include photometry for a large number of observed bands from 4000 Å to 6 μm, as well as rest-frame photometry and other intrinsic properties of the galaxies (e.g. positions, peculiar velocities, stellar masses, sizes, morphologies, gas fractions, star formation rates, metallicities, halo properties). Guo et al. tuned their model to fit the low-redshift galaxy population but noted that at z ≥ 1 it overpredicts the abundance of galaxies below the ‘knee’ of the stellar mass function. Here we extend the comparison to deep galaxy counts in the B, i, J, K and IRAC 3.6, 4.5 and 5.8 μm bands, to the redshift distributions of K and 5.8 μm selected galaxies, the evolution of restframe luminosity functions in the B and K bands and the evolution of rest-frame optical versus near-infrared colours. The B, i and J counts are well reproduced, but at longer wavelengths the overabundant high-redshift galaxies produce excess faint counts. At bright magnitudes, counts in the IRAC bands are underpredicted, reflecting overly low stellar metallicities and the neglect of polycyclic aromatic hydrocarbon emission. The predicted redshift distributions for K and 5.8 μm selected samples highlight the effect of emission from thermally pulsing asymptotic giant branch (AGB) stars. The full treatment of the Maraston model predicts three times as many z ∼ 2 galaxies in faint 5.8 μm selected samples as the model of Bruzual & Charlot, whereas the two models give similar predictions for K-band selected samples. Although luminosity functions are adequately reproduced out to z ∼ 3 in rest-frame B, the same is true at rest-frame K only if thermally pulsating AGB emission is included, and then only at high luminosity. Fainter than L!, the two synthesis models agree but overpredict the number of galaxies, another reflection of the overabundance of ∼1010 M# model galaxies at z ≥ 1. The model predicts that red, passive galaxies should already be in place at z = 2 as required by observations.