Deep optical-NIR imaging of the RO-1001 group from UltraVISTA Ks and J (red and green) and Subaru Suprime-CAM (combined VRI bands; blue), over a 30″ × 40″ field of view. The green contours show the Lyα surface brightness from Fig. 1 in steps of 0.5 dex, from a few 10⁻¹⁷ s⁻¹ erg cm⁻² arcsec⁻² (center) to ×30 lower surface brightness (filaments). The three ALMA/VLA sources are labeled (ABC; white contours), together with a fourth massive galaxy (D) which is a candidate quiescent object in the structure. We note that further luminous objects aligned with the Lyα emission are in the foreground; see e.g., the Lyα depression coincident with the two sources in the East filament, which we interpret as being due to dust absorption.