Faraday dispersion function of disk galaxies with axisymmetric global
  magnetic fields I
  Faraday tomography is a novel method to probe 3-dimensional structure of
magnetic fields of polarized radio sources. In this paper, we investigate
Faraday dispersion function (FDF) of disk galaxies extending a simple analytic
model of galactic magnetic fields developed in Ideguchi et al. (2017). The
model consists of axisymmetric coherent fields and turbulent fields and we
consider the effects of inclination, relative amplitude of coherent and
turbulent magnetic fields and pitch angle of coherent fields. Our simple model
makes it easy to obtain physical interpretation of FDFs and helps understanding
observational results. We find FDFs have two peaks when galaxies are observed
with non zero inclination. The gap and relative height of two peaks are
dependent on the inclination angle and pitch angle but are not affected by
relative amplitude of coherent and turbulent magnetic fields so much. These
findings give us an important caution that two peaks in observed FDFs do not
necessarily imply the presence of two separate radio sources within a beam.
