Rectangular maps of the reconstructed magnetic field and the corresponding uncertainty quantification. The left column shows the mean of the posterior magnetic field distribution across the stellar surface, in terms of the radial (top), meridional (middle) and azimuthal (bottom) magnetic field components. The field strength is given in kG. The grey transparent rectangle indicates the part of the stellar surface that is obscured from view. The right column shows the corresponding standard deviation maps. The results were obtained using a statistical model with hyperparameters Ω_i,i = ηl_i² and η = 100 in the marginal prior distribution for each spherical-harmonic coefficient z_i. Note that the contour plots in this paper consistently use the same number of levels between the minimum and maximum values in all figures.