Conversion factor α_[C II] in our simulated galaxies as a function of gas metallicity (panel a), the SFR averaged over the last 5 Myr (panel b), the SFR averaged over the last 200 Myr (panel c), and the SFR change diagnostic R_{5 − 200} (panel d, see text) at different redshifts. The coloured symbols represent the median α_[C II] in each bin, while the error bars represent the 16–84 percentiles. The Spearman’s rank correlation coefficient between the variables on the y and x axes are shown in each panel as well. The grey dotted line denotes the mean α_[C II] from Zanella et al. (2018) and the shaded band represents the corresponding scatter.