RMs in the first panel (top) were obtained via linear fit (χ = χ₀ + RM λ²) if more than two data points were available. There are several large uncertainties (σ_RM ≳ |RM|) attributed mainly to a significant deviation in χ_obs to a linear relation. From the second to the last panels, RMs were calculated in pairs of 22–43 GHz (second), 43–86 GHz (third), and 86–129 GHz (bottom). RM signs are shown in color: blue and red for negative and positive signs, respectively. The filled and open circles in the first panel indicate the number of frequencies used in the fitting, four and three data points, respectively. Each shaded area is the same as in Figure 1.