Top: comparison between the gas spatial distribution of the J = 2–1 CS and SiO emission in orange and blue contours, respectively, and the dust distribution reported in Mauron & Huggins (1999) as seen in V +B, where the dark arcs and shells trace the location of the dust (background image in black and white colour scale). The small crosses in the image are also from Mauron & Huggins (1999), and represent the emission peaks of other molecular tracers, namely CN, HNC, and HC₃ N reported in Lucas et al. (1995) and Lucas & Guélin (1999). Bottom: same contours representing J = 2–1 CS and SiO emission, with J = 2–1 CS contours in red (changed to improve the visualisation) and J = 2–1 SiO in blue, plotted over C₃N N = 10–9 (black contours) and CN N = 1–0 (background image in pink colour scale) as reported by Agúndez et al. (2017). We note that the spatial scale between both figures is different.