contribute to the FDF of the same value of a Faraday depth.

The right panels show the polarization angle (top) and the FDF (bottom). We can see that the absolute value of the FDF has a main peak at $\phi = -5 ~{\rm rad/m^2}$ and sub peaks at $\phi = -13$ and $-1~{\rm rad/m^2}$ with different polarization angles each other. The main and two sub peaks can be attributed to the emissions in the mid plane at $z\sim 0$, the halo with $z>0$, and the halo with $z<0$, respectively, as implied by the relation between $\phi$ and $z$ (the bottom-left panel). As expected, although polarized intensities are small in the halo, we can see them in the FDF as large peaks because they are accumulated to relatively large values at $\phi = -13$ and $-1~{\rm rad/m^2}$.

Since the sign of the LOS component of magnetic fields can change, in general, Faraday depth does not vary monotonically with the physical distance. Figure \[fig:f2\] represents a less simple case. Again, the bottom-left panel shows that the polarized intensity is peaked at the mid-plane with tails in the halo, but the behavior of the Faraday depth is no longer monotonic with respect to 