Colour composite image of NGC 1566 based on six different HST WFC3/UVIS filters Lee et al. 2023. The middle panel illustrates offsets in the western arm of NGC 1566 between molecular gas (CO, greyscale on background image) and star formation (Hα, green contours). Blue shaded ellipses indicate two reference radial bins (R = 3 kpc and R = 5 kpc), the arrows indicate the sense of rotation, and white contours delimit the spiral mask. In the right panel, the radial distribution of all CO-Hα offsets across the entire NGC 1566 are shown. The first spiral arm is the eastern arm; the second spiral arm is the western arm. The error bars are comparable to the size of the plotted circles. The gray squares show running means at radial intervals of 2 kpc (combining both arms).