Estimates of the Galactic contribution under the “polar caps” data split and comparison to the results of Oppermann et al. (2012). Left column: dimensionless Galactic signal field s, right column: the physical Galactic Faraday depth φ_g in units of rad/m². Top row: posterior mean estimates derived with the “polar caps” split, second row: pixel-wise uncertainty of this estimate, third row: result of Oppermann et al. (2012), and bottom row: result of subtracting the third row from the top row.