Faint galaxy counts and diffuse backgrounds in the submm/mm range

Abstract

A second generation of satellites, like the COBRAS/SAMBA project studied at ESA, would observe the anisotropies of the CMBR on sub‐degree scales, where the contamination of fluctuations due to various foregrounds and backgrounds is important. In particular, it is necessary to estimate the contribution of the diffuse background of unresolved galaxies. For that purpose, this paper proposes a new modelling of the evolution of the IR to mm properties of galaxies which includes the following series of physical processes: growth of linear perturbations (gravitationally dominated by dark matter), non‐dissipative collapse and virialization of haloes, shock‐heating and subsequent cooling and dissipative collapse of baryonic gas, formation of a rotationally‐supported disk‐like core, star formation and stellar evolution, stellar feedback, stellar emission, absorption of star light by dust and re‐emission from the IR to the mm. The model reproduces the IRAS luminosity functions and deep galaxy counts, and gives predictions of the faint galaxy counts and diffuse background of unresolved galaxies in the IR and submm/mm ranges, which are compared with the present upper limits. Finally, we show examples of sky simulations using this new model of galaxy evolution.