PI relation at a wavelength of 1.3 mm for the entire dust emission map (top left) shown in Fig. 6 and the regions of the bridge (top right), D1 (bottom left), and D2 (bottom right). We compare the fitted trends of the PI relation P_frac ∝ I^α for the cases of RAT alignment (long-dashed red), RAT plus scattering (solid blue), and perfect grain alignment (short-dashed black). The gray-scaled counts represent the pixels of the maps in Fig. 6 considering only RAT alignment.