Surface density distribution of the Brγ, H₂ 1−0S(1), and [FeII] emission. From top to bottom, the histograms show the distribution of the surface density in solar units per unit of area (pc²) of the lines measured in the nucleus (defined by aperture “A” in Figs. 1 and 2), the integrated FoV, and the peak of the Brγ (Paα) emission. For the distributions of the ionised gas (first column), we have also included the Paα emission in light blue for the ULIRGs. The Brγ (Paα) peak coincides with the nucleus in ~33% of the LIRGs and in the ~71% of the ULIRGs.