Normalized histograms of p² over SGC34 at 353GHz. Planck data, , blue inverted-triangles, with 1σerror bars as described in text. The pixel density on the y-axis is the number of pixels in each bin of p² divided by the total number of pixels over SGC34. Dust model, , black circles connected by line, with 1σ error bars computed from 100Monte-Carlo realizations. The vertical dashed line corresponds to the parameter p₀ = 18.5% () of this dust model.