Comparison of the total intensity, the polarized intensity (PI) and the polarization angle ( χ) in the nuclear region at 43 and 86 GHz. The maps are restored with the same VLBA 43 GHz CLEAN beam and displayed over the same RA and Dec ranges (±0.5 mas). The arrows show the polarized component identifications. Panel a: as in the central panel of Fig. 2 (43 GHz) but zoomed into the core. Panel b: GMVA 86 GHz total and linear polarization image restored with the VLBA 43 GHz beam. The contours start at 6 mJy beam⁻¹ and increase by a factor of two from the lowest level. The color scale starts from 24 mJy beam⁻¹.