Evaluating and Improving Semi-analytic modeling of Dust in Galaxies
  based on Radiative Transfer Calculations II: Dust Emission in the Infrared
  Interstellar dust grains are responsible for modifying the spectral energy
distribution (SED) of galaxies, both absorbing starlight at UV and optical
wavelengths and converting this energy into thermal emission in the infrared.
The detailed description of these phenomena is of fundamental importance in
order to compare the predictions of theoretical models of galaxy formation and
evolution with the most recent observations in the infrared region. In this
paper we compare the results of GRASIL, a code explicitly solving for the
equation of radiative transfer in a dusty medium, with the predictions of a
variety of IR template libraries. We employ star formation history samples
extracted from the semi-analytical galaxy formation model MORGANA to create
libraries of synthetic SEDs from the near- to the far-infrared. We consider
model predictions at different redshift ranges to explore any possible
influence in the shape and normalization of the SEDs due to the expected
evolution of the galaxy properties. We compute the total absorbed starlight
predicted by GRASIL at optical wavelengths to statistically compare the
synthetic SEDs with the selected IR templates. We show that synthetic SEDs at a
given total infrared luminosity are predicted to be systematically different at
different redshift and for different properties of the underlying model galaxy.
However, we determine spectral regions where the agreement between the results
of radiative transfer and IR templates is good in a statistical sense (i.e. in
terms of the luminosity functions). Moreover, we highlight some potentially
relevant discrepancies between the different approaches, both in the region
dominated by PAH emission and at sub-mm wavelengths. These results determine
potentially critical issues in the infrared luminosity functions as predicted
by semi-analytical models coupled with different IR flux estimators.
