Sources which were not matched either with the primary or the injected secondary source and hence deemed to be spurious. Top: vanilla pipeline. Bottom: image-subtraction pipeline. The colours correspond to the magnitude range of the primary sources around which these spurious sources were found in the mock data. The black points are spurious sources found in the real data. Many of these are likely to be real sources. The horizontal lines of dots are likely to be the same sources found on multiple occasions as the same primary source may be used more than once with a different injected secondary.