HI contour map of NGC3735 on top of its grayscale Hα map (Vargas et al. 2019). The contours are plotted at the 3 mJy beam⁻¹ level, from every even channel in the HI cube, such that purple-blue colours correspond to the approaching side and orange-red colours correspond to the receding side. The velocity range is about 2380–3000 km s⁻¹. The synthesized beam is shown in the bottom right, and is 66.9 × 37.4 arcsec, with PA = 41.8 deg.