Dependence of the Planck correlation ratios with the mean column density of the region on which they are computed in the first multipole bin (ℓ = [50,160]). The HM and DS measurements can be compared to the theoretical expectations (including dust and CMB, as in Eq. (5)) shown as blue segments. The grey bars give the 68% and 95% confidence levels computed over 1000 realizations of dust, CMB, and Gaussian noise. The column density dependence fit by a power law (see Eq. (6)) is shown as a dashed line.