Signal-to-noise ratio per pixel in the original, unsmoothed data, over the region of the RO-1001 nebula within the area where a detection is found in the adaptively smoothing map, shown by color coding in the image (right scale). The flux error in each pixel is already enlarged to account for correlated noise (see Sect. 2). ALMA continuum sources are shown as black contours. White contours show the Lyα surface brightness levels from Fig. 2.