Left: SDC18 SiO (2–1) integrated intensity map from the IRAM-30m. The 3σ intensity level is marked by the black contour. Red contours show the same JCMT total intensity levels of 50, 500, and 1000 mJy/beam as in panel (a) in Figure 2. Right: Spectra extracted from several positions marked by the black dashed lines. In the upper two panels, the red lines are the single-Gaussian fits, while in the bottom panel, the red line is the combination of a two-component Gaussian fit including a broader and narrower component in green and blue, respectively.