Left panels – intensity maps of [C II] 158 μm (top) and ¹²CO J = 13–12 (bottom) in M17 SW, integrated in the velocity ranges 0–40 km  s^-1 and 14–28 km  s^-1, respectively. The contour levels are the 10%, 25%, 50% (thick line), 75% and 90% of the peak emission. Dashed lines are the strip lines shown in Fig. 2. The central position (0′′, 0′′) is marked with a cross. The ultracompact H II region M17-UC1 and four H₂O masers (Johnson et al. 1998) are marked by the black circle and plus symbols, respectively. Right panel – 21 cm continuum emission by Brogan & Troland (2001) with the overlaid contours of the velocity integrated (same as above) emission of ¹²CO J = 13–12 (green), [C II] (red), and the [C I]  370 μm (blue, integrated in 9–30 km  s^-1) from Pérez-Beaupuits et al. (2010). The contour levels (from thin to thick) are the 50%, 75% and 90% of the peak emission. The stars indicate the O and B ionizing stars (Beetz et al. 1976; Hanson et al. 1997). Dashed frames depict the beam center for the edges of the 6 OTF strips. Contour maps are smoothed to 20′′ resolution.