Preferred axis of CMB parity asymmetry in the masked maps
  Both WMAP and Planck data show a significant odd-multipole preference in the
large scales of the cosmic microwave background (CMB) temperature anisotropies.
If this pattern originates from cosmological effects, then it can be considered
a crucial clue for a violation in the cosmological principle. By defining
various direction dependent statistics in the full-sky Planck 2015 maps (see,
for instance, Naselsky et al. (2012); W. Zhao (2014)), we found that the CMB
parity asymmetry has a preferred direction, which is independent of the choices
of the statistics. In particular, this preferred axis is strongly aligned with
those in the CMB quadrupole and octopole, as well as that in the CMB kinematic
dipole, which hints to their non-cosmological origin. In realistic
observations, the foreground residuals are inevitable, and should be properly
masked out in order to avoid possible misinterpretation of the results. In this
paper, we extend our previous analyses to the masked Planck 2015 data. By
defining a similar direction dependent statistic in the masked map, we find a
preferred direction of the CMB parity asymmetry, in which the axis also
coincides with that found in the full-sky analysis. Therefore, our conclusions
on the CMB parity violation and its directional properties are confirmed.
