Cumulative distribution of the integrated intensity of the velocity offsets with respect to spiral arms (ΔV; left) and cumulative distribution normalised by the total flux in their respective datasets (right). In the panels, we show cumulative distribution from the different methods described in the text: direct integration of the original lv−map data cube (orange full line), integration of the lv−map generated by cloud masks (blue dotted-dashed line), integration of the cloud fluxes as per their cloud velocity centroid association to the closest spiral arm (blue dotted lines). The dashed green line shows the 10 km s⁻¹ width used to define arm association.