Metal mass, M_Z, ISM, vs. [C II] luminosity, L_[CII]. The observed galaxy samples at z ≈ 0 (see text) with direct measurements of M_Z, ISM and L_[CII] are shown by the blue circles. The grey- and orange-shaded 2D hexagonal histograms represent simulated galaxies from SÍGAME-v2 (z ≈ 6) and v3 (z ≈ 0), and their mean and 1σ distributions are marked by the grey and orange squares respectively. The dashed line indicates the best-fit relation log(M_Z, ISM/M_⊙) = log(L_[CII]/L_⊙)−0.45 between all data sets and the grey-shaded region indicates the 0.4 dex rms scatter.