(Left) Evolution up to zs2.3 of the comoving number density of “normal” galaxies (i.e. 10⁷      L_⊙ < L_ir < 10¹¹   L_⊙; black filled triangles), LIRGs (orange filled diamonds) and ULIRGs (red filled stars). The green circles represent the total number of galaxies which are above the 24 μm detection limit of the surveys presented here, i.e. . The zs0 points are taken from Sanders et al. (2003). (Right) Evolution of the comoving IR energy density up to zs2.3 (upper striped area) and the relative contribution of “normal” galaxies (yellow filled area), LIRGs (orange filled area) and ULIRGs (red filled area). The areas are defined using all the solutions compatible within 1σ with the infrared LF. Black arrows show the comoving IR energy density derived by stacking the 70 μm image at all IRAC sources positions (Jy). The axis on the right side of the diagram shows the evolution of the SFR density under the assumption that the SFR and L_IR are related by Eq. (3) for a Salpeter IMF.