How sensitive are predicted galaxy luminosities to the choice of stellar population synthesis model?

Abstract

We present a new release of the GALFORM semi-analytical model of galaxy formation and evolution, which exploits a Millennium Simulation-class N-body run performed with the Wilkinson Microwave Anisotropy Probe 7 cosmology. We use this new model to study the impact of the choice of stellar population synthesis (SPS) model on the predicted evolution ofthe galaxy luminosity function. The semi-analytical model is run using seven different SPS models. In each case, we obtain the rest-frame luminosity function in the far-ultraviolet, optical and near-infrared (NIR) wavelength ranges. We find that both the predicted rest-frame ultraviolet and optical luminosity function are insensitive to the choice of SPS model. However, we find that the predicted evolution of the rest-frameNIR luminosity function depends strongly on the treatment of the thermally pulsating asymptotic giant branch(TP-AGB) stellar phase in the SPS models, with differences larger than a factor of 2 for model galaxies brighter than MAB(K) - 5 log h < -22 (̃L* for 0 ≤ z ≤ 1.5). We have alsoexplored the predicted number counts of galaxies, finding remarkable agreement between the results with different choices of SPS model, except when selecting galaxies withvery red optical-NIR colours. The predicted number counts of these extremely red galaxiesappear to be more affected by the treatment of star formation in discs than by the treatment of TP-AGB stars in the SPS models. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.