Redshift evolution of the star formation rate density. Model predictions (coloured lines) are compared with observational data (grey points) coming from Hopkins & Beacom (2006), Bouwens et al. (2011), and Cucciati et al. (2012). Solid lines present the star formation rates derived from the models. They are computed as the sum of the star formation rate of all galaxies and divided by the box volume ((100 /h)³ ≃ 150³ Mpc³). Dashed lines show the merger-driven star formation activity. The bottom panel gives the redshift evolution of the ratio ρ_sfr,burst/ρ_sfr,tot. We can see that the fraction of star formation activity linked to merger events is larger in m₄ than in the reference model m₁.