Image of the polarization structure of the AGN in galaxy M87. The blue scale corresponds to the mapping of the linear polarization intensity. The red lines show the EVPA, with lengths proportional to the polarization intensity. The contours quantify the total intensity (Stokes I). The contours are spaced logarithmically between the image peak (1.21 Jy beam⁻¹) and 0.325 mJy beam⁻¹, which corresponds to the root-mean-squared (rms) of the image residuals. The dashed contour marks the first negative contour in total intensity, at -0.325 mJy beam⁻¹. The full width at half maximum (FWHM) of the convolving Gaussian beam is shown at the bottom-left corner. An alternative version of this figure can be found in Goddi et al. (2021).