For each quasar of the sample, the C IV forest (light blue) and proximity zone (dark blue) are shown. Intrinsic absorbers are reported in different colours according to the different transitions. In particular, we highlight C IV+N V absorbers in yellow, C IV absorbers in red and N V absorbers in green. Blue filled triangles identify those quasars with ALMA observations and [C II] detection at S/N ≥ 5, while empty triangles refer to [C II] non-detections (see Sect. 3 for more details).