Left: 1D PDF of CN (1–0) line intensity, comparing the full dataset PDF (thick dashed black line), the contribution of each of the groups defined in Sect. 5.3 (coloured thick lines), and the contribution of each individual cluster (thin coloured lines). The contributions of clusters are coloured according to the group to which they belong. For readability, we have separated groups CN-1 and CN-2 and their constitutive clusters (top panel) and groups CN-3 to CN-5 and their constitutive clusters (bottom panel). Right: map of the 5 groups resulting from the grouping of consecutive clusters described in the text (Sect. 5.3).