Postage stamps of 10 × 10 arcsec from HST-WFC3 at 0.606 μm to VLA at 5 cm, for the four optically-dark galaxies discussed in Sect. 7. For the two ALMA images at 1.1 mm, those marked by ¹correspond to the non-tapered images, those marked by ²correspond to the 0″60-mosaic images. The K_s-band thumbnail comes from the super-deep detection image described in Sect. 2.4.1. All images are centered on the ALMA detection. We indicate with white arrows the position of the previously associated HST counterpart.