Postage stamps of 1.8 × 1.8 arcsec. ALMA contours (4, 4.5 then 5–10-σ with a step of 1-σ) at 1.1 mm (white lines) are overlaid on F160W HST/WFC3 images. The images are centered on the ALMA detections. The shape of the synthesized beam is given in the bottom left corner. Astrometry corrections described in Sect. 4.3 have been applied to the HST images. In some cases (AGS1, AGS3, AGS6, AGS13, AGS21 for example), the position of the dust radiation matches that of the stellar emission; in other cases, (AGS4, AGS17 for example), a displacement appears between both two wavelengths. Finally, in some cases (AGS11, AGS14, AGS16, and AGS19) there are no optical counterparts. We will discuss the possible explanations for this in Sect. 7.