The insight into the dark side. I. The pitfalls of the dark halo
  parameters estimation
  We examined the reliability of estimates of pseudoisothermal, Burkert and NFW
dark halo parameters for the methods based on the mass-modelling of the
rotation curves.To do it we constructed the $\chi^2$ maps for the grid of the
dark matter halo parameters for a sample of 14 disc galaxies with high quality
rotation curves from THINGS. We considered two variants of models in which: a)
the mass-to-light ratios of disc and bulge were taken as free parameters, b)
the mass-to-light ratios were fixed in a narrow range according to the models
of stellar populations.
  To reproduce the possible observational features of the real galaxies we made
tests showing that the parameters of the three halo types change critically in
the cases of a lack of kinematic data in the central or peripheral areas and
for different spatial resolutions.
  We showed that due to the degeneracy between the central densities and the
radial scales of the dark haloes there are considerable uncertainties of their
concentrations estimates. Due to this reason it is also impossible to draw any
firm conclusion about universality of the dark halo column density based on
mass-modelling of even a high quality rotation curve. The problem is not solved
by fixing the density of baryonic matter.
  In contrast, the estimates of dark halo mass within optical radius are much
more reliable. We demonstrated that one can evaluate successfully the halo mass
using the pure best-fitting method without any restrictions on the
mass-to-light ratios.
