The 21cm radiation from minihalos as a probe of small primordial non-Gaussianity

TL;DR

This paper proposes using 21cm radiation from high-redshift minihalos to detect small primordial non-Gaussianity, showing a significant brightness temperature enhancement for f_NL ≤ 1, which can be observed with future radio telescopes.

Contribution

It introduces a novel method to probe small primordial non-Gaussianity through 21cm signals from minihalos, emphasizing the impact of nonlinear bias on brightness temperature fluctuations.

Findings

Brightness temperature fluctuations are significantly enhanced by small non-Gaussianity.

Results are robust against variations in minihalo formation models.

Sensitivity to strong radiation sources affects the detectability.

Abstract

We present a new probe of primordial non-Gaussianity via the 21cm radiation from minihalos at high redshifts. We calculate the fluctuations in the brightness temperature (measured against the cosmic microwave background) of the 21cm background from minihalos containing HI at redshift \sim 6-20, and find a significant enhancement due to small non-Gaussianity with amplitude f_NL \leq 1. This enhancement can be attributed to the nonlinear bias which is strongly increased in the presence of non-Gaussianity. We show that our results are robust against changes in the assumed mass function and some physical aspects of minihalo formation, but are nevertheless sensitive to the presence of strong radiation sources within or around the minihalos. Our findings are relevant for constraining and searching for small primordial non-Gaussianity with upcoming radio telescopes such as LOFAR and SKA.