Upper: Zoomed-in image of the SO ring-like structure of Oph IRS 63. Middle: Best-fit elliptical ring, as described in Sect. A. Lower: Residuals of the SO emission after subtracting the fitted elliptical ring. The dashed cyan line marks the fitted ridge of the elliptical ring. The white lines indicate the four spiral-like structures (see Fig. 1). Note that the field of view in these panels is smaller than in Fig. 1.