Maximum posterior amplitude polarization maps derived from the Planck observations between 30 and 353 GHz. Left and right columns show the Stokes Q and U parameters, respectively, while rows show, from top to bottom, CMB, synchrotron polarization at 30 GHz, and thermal dust polarization at 353 GHz. The CMB map has been highpass-filtered with a cosine-apodized filter between ℓ = 20 and 40, and the Galactic plane (defined by the 17% CPM83 mask shown in Fig. 41) has been replaced with a constrained Gaussian realization (Planck Collaboration IX 2016).