Molecular clouds have power-law PDFs (not log-normal)

Contrary to common belief, the column density PDFs of molecular clouds are not described well by log-normal functions, but are instead power-laws with exponents close to two. We argue that the intrinsic functional form of the PDF cannot be securely determined below A K ∼ 0.1-0.2 mag, limiting our ability to investigate more complex models for the shape of the cloud PDF.