Modelling infrared galaxy evolution using a phenomenological approach

To characterize the cosmological evolution of the sources contributing to the infrared extragalactic background, we have developed a phenomenological model that constrains in a simple way the evolution of the galaxy luminosity function with redshift, and fits all the existing source counts and redshift distributions, cosmic infrared background intensity and fluctuation observations, from the mid-infrared to the submillimetre range. The model is based on template spectra of starburst and normal galaxies, and on the local infrared luminosity function. Although the cosmic infrared background can be modelled with very different luminosity functions as long as the radiation production with redshift is the right one, the number counts and the anisotropies of the unresolved background imply that the luminosity function must change dramatically with redshift, with a rapid evolution of the high-luminosity sources (L > 3 × 10 11 L� ) from z = 0t oz = 1, which then stay rather constant up to redshift z = 5. The derived evolution of the infrared luminosity function may be linked to a bimodal star formation process: one associated with the quiescent and passive phase of the galaxy evolution, and one associated with the starburst phase, triggered by merging and interactions. The latter dominates the infrared and submillimetre output energy of the Universe. The model is intended as a convenient tool to plan further observations, as illustrated through predictions for Herschel, Planck and ALMA observations. Our model predictions for given wavelengths, together with some useful routines, are available for general use.