Hα luminosity density as a function of the Hα luminosity for local U/LIRGs and distant massive SFG with a similar luminosity range and observed under similar linear resolution conditions. Symbols are the same as in Fig. 3. The histograms for the local (green) and high-z (red) samples are normalized to the total number of objects in each sample. The blue cross in the lower-right corner indicates the typical errors.