High-angular resolution maps from Planck-HFI 857 GHz around the positions of the three studied regions. In the case of the ρ Ophiuchi and Perseus molecular clouds we indicate the positions of different compact clouds extracted from different catalogues and the location of the main ionising star. In W43 we indicate the positions of the molecular clouds identified in the CO survey of Solomon et al. (1987), highlighting in red the two most massive ones. The solid circle delineates the aperture used for flux density integration and the dashed circles enclose the ring used for background subtraction (see Sect. 4.1).