A new model of galaxy formation: How sensitive are predicted galaxy
  luminosities to the choice of SPS model?
  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 WMAP7 cosmology. We use this new model to study the
impact of the choice of stellar population synthesis (SPS) model on the
predicted evolution of the 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-ultra-violet, optical and
near-infrared (NIR) wavelength ranges. We find that both the predicted
rest-frame ultra-violet and optical luminosity function are insensitive to the
choice of SPS model. However, we find that the predicted evolution of the
rest-frame NIR 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 $M_{\rm AB}(K)-5$log$h<-22$ ($\sim$L$_*$ for $0\leq z\leq 1.5$). We have
also explored the predicted number counts of galaxies, finding remarkable
agreement between the results with different choices of SPS model, except when
selecting galaxies with very red optical-NIR colours. The predicted number
counts of these extremely red galaxies appear to be more affected by the
treatment of star formation in disks than by the treatment of TP-AGB stars in
the SPS models.
