From left to right: longitude-velocity diagrams of the number of ¹²CO lines, the brightness temperature ratio of ¹²CO to ¹³CO, and the ¹²CO line width. For each (l,v) pixel, the number of lines is summed over latitudes while the two other quantities are averaged. The maps have been smoothed with a Gaussian kernel of 2 pixels in standard deviation for display. The contours give the outline of the two components separated by hierarchical clustering using these three parameters maps as input. Pixels outside of the contour are associated with the CMZ, and those inside are associated with the disk, if they also verify the other conditions described in the text (see Sect. 3.2).