LBC colour images of the rejected or unclassified fields of Sect. 6.5. We assigned r-SLOAN and z-SLOAN images from the LBC to the blue and red channel of the colour image. The green channel was created from the mean of both bands. Blue dashed lines are the contours from the X-ray emission, but not at the same flux levels for all subimages. North is up, east is left, and the images are centred on the respective X-ray position.