Ionized bubble number count as a probe of non-Gaussianity
  The number count of ionized bubbles on a map of 21 cm fluctuations with the
primordial non-Gaussianity is investigated. The existence of the primordial
non-Gaussianity modifies the reionization process, because the formation of
collapsed objects, which could be the source of reionization photons, is
affected by the primordial non-Gaussianity. In this paper, the abundance of
ionized bubbles is calculated by using a simple analytic model with the local
type of the primordial non-Gaussianity, which is parameterized by f_{NL}. In
order to take into account the dependence of the number count on the size of
ionized bubbles and the resolution of the observation instrument, a threshold
parameter B_b which is related to the the surface brightness temperature
contrast of an ionized bubble is introduced. We show the potential to put the
constraint on f_{NL} from the number count by future observations such as LOFAR
and SKA.
