Modelling Cosmic Infrared Background with evolving galaxies.

Sensitivity of future far infrared space telescopes like Millimetron will be limited by a confusion noise created by distant galaxies. We construct a model of the Cosmic Infrared Background (CIB) aimed at exploration of methods of prediction and reducing the confusion noise. The model is based on a public available eGALICS simulation. For each simulated galaxy we construct a spectral energy distribution with the help of public GRASIL and CHE_EVO codes. In this paper, in order to put our model in the context of current CIB investigations, we compare the outputs of the model: luminosity and mass functions, source counts as a function of flux and redshift, spectrum of the CIB, prediction of confusion limit, with the available observational data and with three other models: one is a well known `backwards evolution' model of Bethermin et al. 2011 and two others are based on a simple mass-luminosity (M-L) relation applied to simulated dark matter halo catalogues. We conclude that our model reproduces the observational data reasonably well. All four models show significant differences in the predictions of the distribution of sources on the flux-redshift plane, especially at high redhifts. The predicted confusion noise on the wavelengths 70--350 microns is consistent between models, while for 650--2000 microns there are significant differences and M-L models should not be used.