NGC 4013 images from RM-synthesis. Top: total intensity color image with polarization contours at 3, 9, 12σ levels with σ of 11.6 μJy. Magnetic field orientations are shown in black. Bottom: RM map of NGC 4013 from C-band on Stokes I contours with a uv-taper of 12 kλ and Gaussian smoothing resulting in a beam size of 18″ × 18″. Contours start at the 3σ level with a σ of 15.0 μJy beam⁻¹ and increase in powers of 2 (up to 256). The RM map is cut at the 3σ level of 35 μJy beam⁻¹ of the polarized intensity map. The mean RM error is 25 rad m⁻².