Left: low resolution (20″) VLA L-band image of MACS J0717+3745. The low surface brightness emission visible at 144 MHz, to the west of the cluster, is also clearly recovered in the VLA L-band image. Contour levels are drawn at [1, 2, 4, 8, …] × 3.0σ_rms, where σ_rms = 14 μJy beam⁻¹. In this image, there is no region below −4σ_rms. The beam size is indicated in the bottom left corner of the image. Right: box distribution across the halo overlaid on the LOFAR total intensity map at 8″ resolution (gray) and polarization contours (blue) at 3 GHz. The cyan boxes show polarized patches found in the halo region. The width of the boxes used to extract the indices is 8″, corresponding to a physical size of about 50 kpc.