Map of G₀ in NGC 7023 NW (color scale). The H₂ S(3) integrated intensity is shown for reference (linear steps of 1.7 × 10^-7 W m^-2 sr^-1). The values of G₀ between the star and the PDR were obtained assuming geometrical dilution of the stellar radiation field and a local extinction value of A_V = 1.5. Inside the PDR, we used the fraction of carbon locked in eVSG as a probe for G₀ (Pilleri et al. 2012).