Ionized bubble number count as a probe of non-Gaussianity

Abstract

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.