Density map of the CFHT/MEGACAM 1°  ×  1° field around CL1411.1−1148. The colour-coding indicates the log₁₀ of the density of galaxies averaged over the ten nearest neighbours. Black contours are at 1 and 3σ above the field mean density. The grey points identify all galaxies with a z_spec within 5σ_cl of the cluster redshift. The inner and outer white circles are positioned at R₂₀₀ and 5R₂₀₀ radius, respectively. The grey bands indicate the gaps between the MEGACAM CCDs. The green circles show our ALMA targets. The thick black outline identifies the two cluster members detected at 24 μm by Spitzer. The pink outer rings show the position of the galaxies with low gas fraction (see Fig. 9 and Sect. 4.2).