Left: SPHERE Q_ϕ image as described in Fig. 2 but with a Gaussian kernel of size 0.2 × FWHM with the spiral arms retrieved from both the ALMA and this image overplotted. Right: ALMA continuum image generated as described in the Appendix C, with the overplotted spiral arms retrieved from both the SPHERE Q_ϕ and this image. The “N” and “S” indicate the northern and southern spirals, respectively.