Distribution of the “clean” GOODS–Herschel and Spitzer-MIPS 24 μm flux densities as a function of redshift (spectroscopic-filled and photometric-open symbols). Non “clean” galaxies (see Sect. 2.3) are not represented. The average 3-σ depths of the surveys listed in Table 1 are shown with horizontal lines (the dashed lines at 100 and 160 μm represent the shallower GOODS-N depths). Due to local noise variations, some 3-σ sources can be detected below these typical limiting flux densities. Sources above z ~ 3 are not represented due to redshift uncertainties.