Ratio between the concentration C_2   kpc for the Hα and the continuum emission plotted against the log of the infrared luminosity L_IR. Note that there are three points with L_IR < 10¹¹ L_⊙. These are IRAS F01341-3735N (ESO-297-G011), IRAS F09437-0317S (IC 563) and IRAS F18093-5744S (IC 4689). For these multiple systems at least one of the individual galaxies falls outside the LIRG luminosity range. The points are labeled on the basis of our morphological classification. Type 0: blue squares. Type 1: black stars. Type 2: red circles.