Three molecular line transitions of ¹³CO J = 1 − 0, ¹²CO J = 2 − 1 and ¹²CO J = 3 − 2 shown as integrated molecular intensity maps are overlaid with the column density of hydrogen molecules (H₂). The contours are from 20% to 90% of the peak with an adjacent contour interval of 10%. Molecular emissions integrated from −3 km s^-1 to 3 km s^-1 (from the channel maps in Appendix A). The white circle is the location of the stellar cluster NGC 1579 and the two straight lines in the left panel indicate the loci for the position–velocity diagrams in Fig. 7.