Schematic representation of selection of 500 μm-risers in the HeViCS field. Coloured in orange are segments of source extraction prior to using MBB-fitter; these are (from upper left, following the arrows) subtraction of strong cirrus emission; SUSSEXtractor list of initial (threshold = 3) 250 μm detections; and assumed a priori list cleaned from extended sources. Enveloped by smaller black squares are parameters considered for the fitting procedure with MBB-fitter corresponding to all pixels in the map where we have 250 μm detections. Coloured in green are segments of our selection after performing the photometry: MBB photometry (S_250−500) at SPIRE wavelengths using 250 μm priors; parent list of 500 μm-risers (140 sources in total), not cleaned from strong synchrotron contaminants; and the final list (133 in total) of 500 μm-risers after excluding local radio sources. We apply the following selection criteria for the final sample: S₅₀₀ > S₃₅₀ > S₂₅₀, S₂₅₀ > 13.2 mJy, and S₅₀₀ >30 mJy.