Example images for NGC 4654. Left: optical gri image of NGC 4654 from the Sloan Digital Sky Survey (e.g., York et al. 2000; Blanton et al. 2017). The orange box corresponds to the CO image area, and the blue box corresponds to the H I image area. Right: gas surface density maps and asymmetry difference maps for the VERTICO CO image (top, 9″ beam) and the VIVA H I image (bottom, 16.9″ × 16.7″ beam). Overlaid on the gas surface density maps, we show the division between the leading half (shaded) and trailing half (not shaded) for NGC 4654 as used in Sect. 4 (Lee et al. 2022c).