Moment 0 of (a) CH₃OH-E (4_2, 3–3_1, 2), (b) CH₃OH-A (5_1, 4–4_1, 3), (c) CH₃OH-A (8_0, 8–7_1, 7), (d) p-H₂CO (3_0, 3–2_0, 2), and (e) SiO (5–4) lines around the molecular arc (integrated from 0 to +12 km s⁻¹). Cyan lines and arrows follow Fig. 1. The white contours mark the 5σ emission. Small circles indicate the positions of the brightest spots in CH₃OH (4_2, 3–3_1, 2), SiO (5–4), and p-H₂CO (3_0, 3–2_0, 2), which we label “A”, “B”, and “C”, respectively. The red cross indicates the position of SMM 1A (Fig. 1). The green semicircle shows the ALMA Band 6 FoV, while the grey background delimits the region inside each ALMA pointing.