Are polar rings indeed polar?
  We have considered polar ring galaxy candidates, the images of which can be
found in the SDSS. The sample of 78 galaxies includes the most reliable
candidates from the SPRC and PRC catalogs, some of which already have kinematic
confirmations. We analyze the distributions of studied objects by the angle
between the polar ring and the central disk, and by the optical diameter of the
outer ring structures. In the vast majority of cases, the outer structures lie
in the plane close to polar (within 10-20 deg) which indicates the stability of
the corresponding orbits in the gravitational potential of the halo. Moderately
inclined outer structures are observed only in about 6% of objects which
probably indicates their short lifetime. In such an unstable configuration, the
polar ring would often cross the disk of the galaxy, being smaller than it in
the diameter. We show that the inner polar structures and outer large-scale
polar rings form a single family in the distribution of diameters normalized to
the optical size of the galaxy. At the same time, this distribution is bimodal,
as the number of objects with d_ring= (0.4-0.7)*d_disk is negligible. Such a
shape of size distribution is most likely due to the fact that the stability of
polar orbits in the inner regions of galaxies is maintained by the bulge or the
bar, while in the outer regions it is provided by the spheroidal (or triaxial)
halo.
