which various FDFs having peaks at different Faraday depths are mixed together.

Note that the absolute value of the total FDF is not in general equal to the sum of the absolute values of FDFs for the quadrants because the polarization angles are different each other. This is the effect so-called beam depolarization, though it is not so significant at the shown scales because coherent magnetic fields dominate over the turbulent magnetic fields.

FDF and the global properties of galaxy {#subsection:3.2}
---------------------------------------

If the FDF of galaxies can be described with simple functions, we can quantify the FDF easily. However, as shown in the previous subsection, FDFs of galaxies are very complicated in general and it is very difficult to translate them into the distribution of physical quantities in physical space. Nevertheless, it would be possible to extract some global properties of galaxies, such as the average amplitude and the coherence length of magnetic fields and the scale heights of thermal and cosmic-ray electrons. This is because such properties could affect the FDF through the behavior of the Faraday depth as a function of physical distance. Below, we consider statistical properties of FDFs of the whole region for 4 models 