Multiple FUV-illuminated edges in OMC-1 (dense PDRs). The colored map shows the integrated emission (I) of the [¹³C II] (²P_3/2−²P_1/2F = 2–1) line at 1900.466 GHz (Goicoechea et al. 2015). This emission traces the C⁺ layers of the molecular cloud. Cyan contours show a map of the SH⁺ 1₀ − 0₁F = 1/2–3/2 emission at 345.944 GHz (Goicoechea et al. 2021), a proxy of the S⁺ layer (both maps at θ_HPBW ≃ 20″). Black contours show the O I 1.317 μm fluorescent emission that delineates the IF of the Bar (Walmsley et al. 2000). Dashed blue circles show the smallest and largest θ_HPBW of our Yebes 40 m observations toward the DF position: 36″ and 54″, respectively.