Left: rotation measure image calculated with the images at 1443, 1630, 4535, and 4885 MHz smoothed with a FWHM Gaussian of 19′′. The color range is from −60 to 60 rad/m². Contours refer to the total intensity image at 1443 MHz. Levels are 1 (3σ_I), 5, 30, and 100 mJy/beam. Middle: burn law a in rad²/m⁴ calculated with the same images used to derive the RM. The image is derived from a fit of FPOL as a function of λ⁴ following the Eq. (5). The color range is from −500 to 1300 rad²/m⁴. Right: intrinsic polarization (Ψ₀ and FPOL₀), obtained by extrapolating to λ = 0 both the RM (Eq. (3)) and the Burn law (Eq. (5)).