HST/FOC polarization maps of Mrk 3 (observation ID 6702) through filter F342W. Left: Intensity map overlaid with integration regions used in Table 2. Right: Debiased polarization degree. Darker pixels have [S/N]_P < 1. Both maps are shown at a spatial binning 0.05″, smoothed using a 0.075″FWHM Gaussian kernel. 63 pixels have [S/N]_P ≥ 3. The orange cross displays the estimated location for the obscured nucleus (Kishimoto et al. 2002).