Observations of CO and [CI] compared to models. Line observations are given by black circles and corresponding error bars. Yellow swath shows CO SLED for z ∼ 1.5 BzK galaxies from Daddi et al. (2015) for comparison (normalized by CO(1-0) or CO(2-1)). The main figure corresponds to CO observations, while the inset figure corresponds to [CI] (note different axis scale). The LVG best-fit model is shown as a black solid line. The PDR plus shock best-fit model is shown as a solid red line with the contributing PDR and shock components shown as dashed and dash-dotted red lines, respectively. The two-PDR-component best-fit model is shown as a solid blue line with the contributing PDR components shown as dashed and dash-dotted blue lines.