Purity of [CII] detections as a function of the S/N threshold in the moment-0 map. The purity is provided only for the 1 arcsec central region and was estimated using the methods described in Sect. 6.2. The blue solid line is derived using the method based on the moment-0 maps and the red dashed line using an extraction in the negative cubes (see Sect. 6.2). The dotted vertical lines are the S/N at which the 95% purity is reached.