Ionized bubble number count as a probe of non-Gaussianity

TL;DR

This paper explores how counting ionized bubbles in 21 cm maps can serve as a probe for primordial non-Gaussianity, potentially constraining the non-Gaussianity parameter f_{NL} with future radio observations.

Contribution

It introduces an analytic model linking ionized bubble counts to primordial non-Gaussianity, incorporating bubble size and observational resolution effects.

Findings

Ionized bubble counts are sensitive to primordial non-Gaussianity.

Future observations like LOFAR and SKA can constrain f_{NL} using this method.

The model accounts for bubble size and instrument resolution effects.

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.