Number of pixels whose integrated Hα intensity I_Hα (black curve) and integrated CO(2–1) intensity W_CO (blue curve) are above the value given in the bottom abscissa for I_Hα and in the top abscissa for W_CO, for the entire galaxy. Left panel: full range of values in logarithmic scale. Right panel: zoomed-in linear scale. The red dashed lines are as in Fig. 1. The green dashed lines show the values corresponding to 45 pixels (or a surface of about 5) in the Hα map.