Predictions for Herschel from LambdaCDM: unveiling the cosmic star
  formation history
  We use a model for the evolution of galaxies in the far-IR based on the
LambdaCDM cosmology to make detailed predictions for upcoming cosmological
surveys with the Herschel Space Observatory. We use the combined GALFORM
semi-analytical galaxy formation model and GRASIL spectrophotometric code to
compute galaxy SEDs including the reprocessing of radiation by dust. The model,
which is the same as that in Baugh et al. (2005), assumes two different IMFs: a
normal solar neighbourhood IMF for quiescent star formation in disks, and a
very top-heavy IMF in starbursts triggered by galaxy mergers. We have shown
previously that the top-heavy IMF appears necessary to explain the number
counts and redshifts of faint sub-mm galaxies. In this paper, we present
predictions for galaxy luminosity functions, number counts and redshift
distributions in the Herschel imaging bands. We find that source confusion will
be a serious problem in the deepest planned surveys. We also show predictions
for physical properties such as star formation rates and stellar, gas and halo
masses, together with fluxes at other wavelengths (from the far-UV to the
radio) relevant for multi-wavelength follow-up observations. We investigate
what fraction of the total IR emission from dust and of the high-mass star
formation over the history of the Universe should be resolved by planned
surveys with Herschel, and find a fraction ~30-50%, depending on confusion.
Finally, we show that galaxies in Herschel surveys should be significantly
clustered.
