Left – strip lines of the molecular (¹²CO) and atomic ([C I], [C II]) gas at Δδ = 30′′ (PA 90°) across the ionization front of M17 SW. Right – strip lines at PA 63° (Δδ = Δα/2). The lower-J lines of ¹²CO, and [C I] are from Pérez-Beaupuits et al. (2010, their Fig. 3). All these profiles are in units of K  km  s^-1 . The VLA 21 cm continuum and H I optical depth (integrated between 0 and 30 km  s^-1) by Brogan & Troland (2001) are in units of 500 × Jy beam^-1 and 8 × τ(HI) km  s^-1 , respectively. The offset, Δα = 0′′ in RA, is the same as in Fig. 1.