Intrinsic Hα half-light radii (CoG, method) of local U/LIRGs as a function of the infrared luminosity. The symbols indicate different morphological classes: triangles are interacting and pre-coalescence systems, squares are post- coalescense mergers, and circles are isolated disk galaxies. Green symbols are objects included in the subsample for comparison with high-z. The individual galaxies of the system IRAS 06259-4708 (C and S), which also belong to this subsample, are not included in the plot since no values for their L_ir exist. However, considering the total luminosity of the system (log(L_ir/L_⊙) = 11.91) and their Hα luminosities, they are likely LIRGs. Open symbols are used for LIRGs, and solid ones for ULIRGs. Values encircled in blue indicate targets with evidence of hosting a (weak) AGN according to their optical spectra (see Table 2). For unresolved systems, upper limits are represented. For some low luminosity objects, the values represented are lower limits owing to the limited FoV. This is illustrated by the arrows, which indicate a factor of 1.5 increase in size. The blue cross in the lower-right corner indicates the typical errors of an object with r_1/2 ~ 2 kpc (for detailed individual errors see Table 2). See text.