Mean [CII] line intensity as a function of the observed frequency (equivalently, emitted redshift). Predictions from our rTNG and AM models are shown by dots and open squares, respectively. Symbols are color-coded according to the used SFR-to-L_[CII] relation, blue symbols for A20, green symbols for L18, and black symbols for V15. L18 is also plotted including the contribution of 3 × 10⁹ − 10¹⁰ M_⊙ halos for our AM model (green x-shaped points) and the TNG100-1 snapshots (green plus-shaped points; see text for more details). Predictions from Yue et al. (2015, yellow line) and Chung et al. (2020, turquoise line) are also shown for comparison.