Left: high-resolution column density PDF of Orion B, derived from the column density map of Fig. 2 left. The lognormal fit (dashed red curve) peaks at 0.92 × 10²¹ cm⁻² in , and has a standard deviation of ~0.25 in log. The power-law fit to the higher column density tail at A_V ≳ 3 (dashed black line) is ΔN/Δlog. The vertical dashed line at A_V ~ 1 marks the lowest closed contour in the column density map. Right: corresponding (normalized) cumulative mass fraction as a function of column density. The dense material above A_V ~ 3–7 mag represents only ~30–13% of the total cloud mass, respectively, as indicated by the two dashed vertical lines. A power-law fit to the cumulative mass fraction for A_V ≳ 3 gives .