All-sky maps, in Aitoff projection, showing the disposition of the 356 bins with latitude | b | ≥ 10°, which are retained for the fitting procedure, together with their average observational Galactic Faraday depth, , after subtraction of the contribution from Wolleben et al.’s (2010) magnetized bubble (top panel). Also shown is the decomposition of into a symmetric part, (middle panel), and an antisymmetric part, (bottom panel). The coordinate system and the color code are the same as in Figs. 1 and 2. The grey band along the Galactic plane masks out the 72 bins with |b| < 10°, which are excluded from the fitting.