Images and spectra highlighting the member galaxies of the CGG-z4 galaxy group. Top left: VISTA Ks images overlaid with cyan SCUBA-2 850 μm contours in steps of 3, 5 and 7σ. Photometric redshift candidate members in the range 4.0 < z < 4.6 are highlighted with red dashed circles. Galaxies with ALMA continuum detections are highlighted as magenta-dashed circles. The green square highlights the region of the right image. Top right: VISTA RGB color images of CGG-z4 at z ∼ 4.3 using the Ks (red), J (green), and i (blue) bands. Two spectroscopically confirmed galaxies have ALMA 3 mm and 870 μm continuum emission shown as green and yellow contours. Contours are shown at levels 5, 7, and 10σ. ALMA beam sizes and an image scale are shown in the lower right corner. The RGB frames are composed using linear scales with identical limits. Bottom: ALMA 3 mm spectra for galaxies with emission line detections. The detected lines are highlighted in yellow with their names labeled. The red line shows Gaussian fits to the CO emission lines and a power law fit to the continuum that increases with frequency following the expression ν^3.7.