Examples of the F356W/F277W/F115W RGB-colour image for both SMGs (left) and field galaxies (right). For the SMGs, we overlay the ALMA 870 μm 11σ contour (purple) from Stach et al. (2019) or Simpson et al. (2020). In the lower panel of each source, we show the residuals of the GALFITM single Sérsic model fit. The blue ellipse marks the region within which we calculate the RFF of the Sérsic fit, as quantified in the lower left corner of each panel. The galaxies are selected to have a m_F444W = 20–22 and are ranked from low-to-high RFF. No clear distinction is identified in the F444W RFF values between the SMGs and field galaxies.