Binned trends of line integrated intensity as a function of column density. The data are binned in 30 equally sized bins of column density. Black circles correspond to the bin average, while the grey shading indicates the standard deviation in each bin. The solid black line is a smoothly varying double PL fit to the trends, specific to each emission line. The dashed red line shows, for comparison, the empirical fit to the Perseus cloud by Tafalla et al. (2021), assuming a kinetic temperature of 11 K. Each panel shows a different emission line: ¹²CO(J = 1 → 0), ¹³CO(J = 1 → 0) and HCO⁺(J = 1 → 0) (left to right, top row); C¹⁸O(J =1 → 0), HCN(J =1 → 0) and ¹²CS(J = 2 → 1) (middle); HNC(J = 1 → 0), SO(J_K = 3₂ → 2₁) and N₂H⁺(J = 1 → 0) (bottom). The standard Milky Way CO-to-H₂ conversion factor and its typical uncertainty (Bolatto et al. 2013) is indicated in the top left panel. An HCN( J = 1 → 0) dense gas conversion factor of 60 M_⊙ (K km s⁻¹)⁻¹ is indicated in the central panel as the green curve.