Rotation measure grid after the subtraction of the Galactic RM Anderson et al. (2021). The images are centered on the Fornax cluster center and go down to a radius of 1.42 deg. Each circle represents a source with the area proportional to the source area, color-coded according to its average RM. The contours refer to the 0.2–2.3 keV e-ROSITA surface brightness image (smoothed at 5′) and start at 3σ with σ = 0.072 counts s⁻¹deg⁻² and scale with $\sqrt{2}$.