Left panel: Lyα (blue) and [C II] (red) profiles of the AzTEC-3+LBG-3 system in velocity space and normalized to the maximum. The [C II] spectrum is taken from Riechers et al. (2014) and it is associated to AzTEC-3 (see Fig. 7). Right panel: normalized [C II] profile (red), Lyα profile of the emission extracted at the position of the main Lyα peak associated to the SMG (blue and black curves), extracted from the position of the rest-frame UV knots of AzTEC-3 as seen in the F160W image (green), and extracted at the position of the main Lyα peak associated to LBG-3 (cyan). The extraction is done in an aperture of 0.7″ radius for the blue, green, and cyan profiles and increasing the S/N of the connected pixels in CubEx for the black profile. For simplicity, we call the spectra as onlySMG Lyα, onlySMG UV knots, and onlyLBG. The normalization of these spectra is performed with the same factor used to normalize the spectrum of the AzTEC-3+LBG-3 system in the left panel to show the different intensities. The normalization of the [C II] profile is also performed accordingly.