Velocity dispersion of the ISM (narrow component) as a function of the star formation density, Σ_SFR, derived considering the extinction corrected Hα fluxes (see text), and Hα half-light radii (Arribas et al. 2012). The symbol and line codes are indicated in the right panel. The black continuous line corresponds to an unweighted regression to all the U/LIRGs (σ, n = 0.06 ± 0.03, r = 0.3), while the dotted and dashed lines are for non-AGNs (n = 0.06, r = 0.4) and AGNs (n = 0.03, r = 0.1), respectively. The shaded region corresponds to a behaviour of the type σ (km s for efficiencies (ϵ) between 100 and 240, which is expected for SF driven motions (Lehnert et al. 2009). The magenta line corresponds to the unweighted) fit, found by Genzel et al. (2011), to a large compilation of high-z galaxies and clumps (see text).