Correlation between the degree of alignment, ξ, and the polarization fraction, p, for the selected pixels, both for data (black squares) and for the Gaussian models. The models are characterized by the following values of σ_M: 15° in green, 29° in red, 33° in magenta and 38° in purple. The data values of p are normalized to the maximum value, p_max, within the sample. For the models, p = cos²γ_M. This figure shows that projection effects, probed by the Gaussian models, are likely to be the main cause of the correlation between ξ and p.