L_{[CI](1 − 0)}/L_{CO(4 − 3)} vs. L_{[CI](1 − 0)}/L_IR in the top panel and L_{[CI](2 − 1)}/L_{CO(7 − 6)} vs. L_{[CI](2 − 1)}/L_IR in the bottom panel for our sample. Our sources are represented as red squares. The SMGs (dark green stars), main-sequence galaxies at z ∼ 1 (indigo hexagons), local galaxies (gold empty circles), and AGNs (grey diamonds) from the Valentino et al. (2020) compilation are plotted along with our sample. The isocontours of density and radiation field intensity are plotted as grey dashed and grey dot-dashed lines, respectively. These isocontours are obtained from the PDR modelling of Kaufman et al. (2006) from the PDR toolbox (Pound & Wolfire 2023). The individual luminosities are not corrected for magnification.