Comparison of the cosmic [C II] luminosity density (ρ_[C II]) for different luminosity cuts in the MARIGOLD simulations with observational estimates from ALPINE (Loiacono et al. 2021) – clustered and field estimates in pink and blue, respectively; from REBELS (Aravena et al. 2024) in purple and from a semi-empirical model by Roy & Lapi (2025) shown as an orange dashed line. The ρ_[C II] from the simulations is obtained by integrating the LFs shown in Fig. 3 down to log(L_min/L_⊙) = 5 (black), 7 (red), and 7.5 (blue). The shaded regions represent the 16–84 percentile range of ρ_[C II] obtained from the LFs.