Structural properties of non-spherical dark halos in Milky Way and
  Andromeda dwarf spheroidal galaxies
  We investigate the non-spherical density structure of dark halos of the dwarf
spheroidal (dSph) galaxies in the Milky Way and Andromeda galaxies based on
revised axisymmetric mass models from our previous work. The models we adopt
here fully take into account velocity anisotropy of tracer stars confined
within a flattened dark halo. Applying our models to the available kinematic
data of the 12 bright dSphs, we find that these galaxies associate with, in
general, elongated dark halos, even considering the effect of this velocity
anisotropy of stars. We also find that the best-fit parameters, especially for
the shapes of dark halos and velocity anisotropy, are susceptible to both the
availability of velocity data in the outer regions and the effect of the lack
of sample stars in each spatial bin. Thus, to obtain more realistic limits on
dark halo structures, we require photometric and kinematic data over much
larger areas in the dSphs than previously explored. The results obtained from
the currently available data suggest that the shapes of dark halos in the dSphs
are more elongated than those of $\Lambda$CDM subhalos. This mismatch needs to
be solved by theory including baryon components and the associated feedback to
dark halos as well as by further observational limits in larger areas of dSphs.
It is also found that more diffuse dark halos may have undergone consecutive
star formation history, thereby implying that dark-halo structure plays an
important role in star formation activity.
