r_CICO as a function of L_IR for our sample of ULIRGs. Similar relations with other galaxy properties are reported in Fig. E.1. Sources with direct measurements of both the [CI](1–0) and CO(1–0) lines are plotted using purple crosses. The pink diamonds represent sources observed in [CI](1–0) but without CO(1–0) line data, for which we inferred from the CO(2–1) line luminosity by assuming r₂₁ = 1.1, which is the mean value computed for our sample (see Fig. 6). The dashed purple line represents the best fit using a least squares regression analysis, and the shaded gray area corresponds to the 1σ confidence interval of the fit. The Pearson correlation coefficients (ρ) are reported at the upper-left corner of the panel with their associated p-values.