Correlation plots extracted from the Orion B maps, convolved to a uniform resolution of 36″ and pixel size of 15″. Dark blue diamonds represent the CO-dark cloud, blue diamonds represent the CO clumps, red squares represent the Horsehead neck, triangles in different shades of green represent the PDRs (bright green is the Horsehead PDR), and yellow triangles represent the H ii region. Edge-on model predictions for selected gas densities are plotted as lines. Dashed lines are for A_V,los = 2.5, with dark gray corresponding to a gas density of n_H = 3.0 × 10³ cm^-3, medium gray to n_H = 1.6 × 10⁴ cm^-3, and light gray to n_H = 4.0 × 10⁴ cm^-3; dotted lines are the same but for A_V,los = 5.0; the medium and light gray dash-dotted lines are for A_V,los = 0.5, with n_H = 1.6 × 10⁴ cm^-3 and n_H = 4.0 × 10⁴ cm^-3, respectively. In panel f, the best fit is plotted as a line.