Left panel: velocity-integrated intensity maps of HCN J = 1 → 0 (grey), HCN J = 3 → 2 (red contour), ¹²CO J = 11 → 10 (green contour), and ¹²CO J = 16 → 15 (blue contour). The contour levels (from thin to thick) are the 50%, 75%, and 90% of the respective peak emissions. The stars on the top left show the location of O and B ionizing stars (Beetz et al. 1976; Hanson et al. 1997). The reference position (Δα = 0, Δδ = 0) is the same as in Fig. 1. The ultracompact H II region M17-UC1 and four H₂O masers (Johnson et al. 1998) are labeled with the (cyan) circle and plus symbols, respectively. The horizontal dashed line depict the strip lines shown in Fig. 5. All maps are convolved to a 30′′ beam to match the resolution of the HCN J = 1 → 0 map. Right panel: velocity-integrated intensity maps of HCN J = 8 → 7 (gray), HCO⁺J = 9 → 8 (red contour), and ¹²CO J = 16 → 15 (green contour). The blue circles correspond to the heavily obscured (E_median> 2.5 keV, A_V ≥ 10 mag) population of X-ray sources around the M17-UC1 region (Fig. 10 in Broos et al. 2007; coordinates from the VizieR catalogue). In this case, all maps were convolved to the beam size () of the ¹²CO J = 16 → 15 map.