Ratio of the strength of the FUV radiation field and volume density (G₀/n) in Orion B, and the distribution of pixels in dense and translucent gas. Top panel: G₀/n at 40 arcseconds (0.08 pc at the distance of the source) across Orion B, where G₀ is in Habing's units and n in units of cm⁻³. Black contour corresponds to ¹³CO integrated intensity of 0.5 K km s⁻¹, indicating the boundaries of a GMC. Dashed contours correspond to values of G₀/n of 1 cm³ (orange) and 20 cm³ (dark red). We divide Orion B in six different regions. The bottom panels show histograms of normalized distribution of pixels having specific dust extinction (left panel), mean volume density (middle panel) and G₀/n (right panel). The orange and purple shaded regions correspond to values of pixels from translucent and dense medium, respectively.