Constraints on Primordial non-Gaussianity from Future HI Intensity Mapping Experiments

TL;DR

Future 21-cm intensity mapping experiments like SKA-I, FAST, and BINGO can significantly improve constraints on primordial non-Gaussianity, especially on the local shape, surpassing current CMB limits with extended observation times.

Contribution

This study forecasts the potential of upcoming HI intensity mapping experiments to constrain all four fundamental shapes of primordial non-Gaussianity, highlighting their competitive advantages over Planck.

Findings

SKA-I can outperform Planck in constraining local non-Gaussianity.

Extended observation time improves constraints on equilateral and orthogonal shapes.

FAST with lower frequency band can achieve constraints better than Planck.

Abstract

The primordial non-Gaussianity induces scale-dependent bias of the \hi with respect to the underlying dark matter, which exhibits features on the very large scales of the 21-cm power spectrum potentially observable with \hi intensity mapping observations. We forecast the prospective constraints on the four fundamental shapes of primordial non-Gaussianity (local, equilateral, orthogonal, and enfolded), with the current and future \hi intensity mapping experiments, BINGO, FAST, and SKA-I. With the current configuration of the experiments and assumed one-year observation time, we find that the SKA-I will provide tighter constraints on the local shape of primoridal non-Gaussianity than Planck. The results are $(\sigma_{f^{\rm local}_{\rm NL}},\sigma_{f^{\rm equil}_{\rm NL}},\sigma_{f^{\rm orth}_{\rm NL}},\sigma_{f^{\rm enfold}_{\rm NL}})_{\rm SKA-I}=(0.54, 86, 25, 43)$, $(\sigma_{f^{\rm local}_{\rm NL}},\sigma_{f^{\rm equil}_{\rm NL}},\sigma_{f^{\rm orth}_{\rm NL}},\sigma_{f^{\rm enfold}_{\rm NL}})_{\rm BINGO}=(17, 100, 128, 164)$, $(\sigma_{f^{\rm local}_{\rm NL}},\sigma_{f^{\rm equil}_{\rm NL}},\sigma_{f^{\rm orth}_{\rm NL}},\sigma_{f^{\rm enfold}_{\rm NL}})_{\rm FAST}=(9.5, 44, 75, 94)$. If the lower frequency band of FAST can be used, the constraint on local-type primordial non-Gaussianity will be $\sigma_{f_\mathrm{NL}}\sim1.62$ which is better than Planck. In addition, if the observation time for FAST could be extended to two years, the constraint on the equilateral shape of primordial non-Gaussianity would be improved to $\sigma_{f_\mathrm{NL}}\sim32$. Similarly, if the observational time of SKA-I could be extended to two years, the constraint on local and orthogonal shapes could be improved to $0.43$ and $20$, respectively, achieving better constraints than Planck.