Density point distribution function (PDF) of the gas for each galaxy type (averaged over the different snapshots). The local spiral and high-z disk models have density PDFs that are well described by a log-normal functional shape, with a small excess of high-density gas in the form of a power-law tail, which corresponds to self-gravitating gas (Renaud et al. 2013; Bournaud et al. 2014). SB mergers strongly deviate for a log-normal PDF and have a strong excess of high-density gas. The rapid drop in the PDFs above 10⁶ cm^-3 corresponds to the resolution limit of our simulations.