A semiempirical model of the infrared universe

We present a simple model of the infrared universe, based as much as possible on local observations. We model the luminosity and number evolution of disk and starburst galaxies, including the effects of dust, gas, and spectral evolution. Although simple, our approach is able to reproduce observations of galaxy number counts and the infrared and submillimeter extragalactic backgrounds. It provides a useful probe of galaxy formation and evolution out to high redshift. The model demonstrates the significant role of the starburst population and predicts high star formation rates at z similar to 3-4, consistent with recent extinction-corrected observations of Lyman break galaxies. Starbursting galaxies are predicted to dominate the current Submillimeter Common-User Bolometer Array surveys. Their star formation is driven predominantly by strong tidal interactions and mergers of galaxies. This leads to the creation of spheroidal stellar systems, which may act as the seeds for disk formation as gas infalls. We predict that the present-day baryonic mass in bulges and halos is comparable to that in disks. From observations of the extragalactic background, the model predicts that the vast majority of star formation in the universe occurs at z less than or similar to 5.