The optically-dark side of galaxy formation

In this letter, we estimate how much starlight was absorbed by dust and released in the infrared during the formation of galaxies. New constraints are set on this so-far hidden history by the recent detection of the Cosmic Infrared Background (CIB) built up from the accumulated light of faint sources (and revisited here). By means of a semi-analytical model of hierarchical galaxy formation, we estimate the population of dust-enshrouded starburst galaxies fitting the CIB. It is argued that a deep ISO survey at 175 micron could already detect these sources and help close the gap in our understanding of the history of light in the Universe.