Ratio between the number of star particles younger than a certain age ($N_{\mathrm{star}}(<t)=M_{\mathrm{star}}(<t)/m_{\ast ,\min }$) and the number of cells containing at least one young star particle with age (N_cell(< t)). We include stars inside the main halo in all snapshots. Simulations with different star formation models and SN energies are shown with different color codes, as indicated in the legend.