Cosmological history of stars and metals

We study the evolution of stellar content and the chemical enrichment of the universe averaged over the whole population of galaxies by means of a series of chemo–spectrophotometric models that take into account the metallicity and dust obscuration effects. We investigate various classes of cosmic star formation rates (CSFR) histories consistent with current estimations. We are able to reproduce a variety of observational constraints such as the emissivities at rest–frame 0.44, 25, 60 and 100 µm of the local universe and also the overall shape of the extragalactic background light from UV/NIR galaxy counts and the cosmic infrared background (CIB) from DIRBE/FIRAS measurements. We find that the CIB at 140 µm is crucial for discriminating between the CSFR histories. The best–fit model to this constraint seems to favour mid–infrared derived CSFR at low–z and a flat CSFR at higher z consistent with the most recent estimations , although the shape of the CSFR at high redshifts has little impact on the FIR/submm part of extragalactic background. We suggest that the bulk of the CIB energy is produced by a population of moderately obscured normal galaxies lying at 0 ≤ z ≤ 1. We then derive the global chemical enrichment and stellar content of the universe and find that this model predicts metallicities in good agreement with the metallicity in DLAs given that some outflow of metal–enriched gas from galaxies is assumed, but it overproduces the current present–day stellar mass density and NIR luminosity density.