Groups of galaxies around ALMA sources (blue squares). The colored triangles indicate the HST-selected galaxies belonging to the same group found around the redshift of ALMA sources (bottom left corner). The two quasars in the MUDF are labeled with red diamonds, the black arrow indicates the QSO sightline in which absorption at the redshift of each group is detected. The black crosses mark the projected location of the galaxy stellar mass-weighted barycenter of the groups. The gray solid and dashed lines report the PB response at 0.3 and 0.5, respectively, of the ALMA band 6 mosaic.