(Left) Selection limits introduced in the T_dust − L_IR parameter space by single-wavelength detection techniques. Continuous, dashed, dotted-dashed, triple-dotted-dashed and dotted lines show the lower limits on L_IR introduced by the submm, PACS, SPIRE, MIPS-24   μm and radio observations, respectively, at z = 1.5 (thin blue lines) and at z = 2.5 (thick red lines). The parameter space reachable by a given single-wavelength detection technique corresponds to the area situated to the right of the lines. As an example, the red arrows show the parameter space probed at zs2.5 by our GOODS-N SMG sample. The shaded area shows the local T_dust − L_IR relation found by Chapman et al. (2003), linearly extrapolated to 10¹³   L_⊙. The striped area presents results for SMGs extrapolated by Chapman et al. (2005) from radio and submm data. (Right) The hatched histogram shows the redshift distribution of our PACS/SPIRE detected SMG sample. The empty histogram shows the redshift distribution of its parent sample, i.e., SMGs with robust redshift estimates obtained through secure multi-wavelength identifications.