Where stars form and live at high redshift: clues from the infrared

The relation between dark matter halos and the loci of star formation at high redshift is a pressing question in contemporary cosmology. Matching the abundance of halos to the abundance of infrared (IR) galaxies, we explore the link between dark matter halo mass (M-h), stellar mass (M-*) and star-formation rate (SFR) up to a redshift of 2. Our findings are five-fold. First, we find a strong evolution of the relation between M-* and SFR as a function of redshift with an increase of sSFR = SFR/M-* by a factor similar to 30 between z = 0 and z = 2.3. Second, we observe a decrease of sSFR with stellar mass. These results reproduce observed trends at redshift z > 0.3. Third, we find that the star formation is most efficient in dark matter halos with M-h similar or equal to 5 x 10(11) M-circle dot, with hints of an increase of this mass with redshift. Fourth, we find that SFR/M-h increases by a factor similar to 15 between z = 0 and z = 2.3. Finally we find that the SFR density is dominated by halo masses close to similar to 7 x 10(11) M-circle dot at all redshift, with a rapid decrease at lower and higher halo masses. Despite its simplicity, our novel use of IR observations unveils some characteristic mass-scales governing star formation at high redshift.