Full-sky bispectrum in redshift space for 21cm intensity maps

Understand

We compute the tree-level bispectrum of 21cm intensity mapping after reionisation.

• We work in the directly observable angular and redshift space, focusing on equal-redshift correlations and thin redshift bins, for which the lensing contribution is negligible.
• We demonstrate the importance of the contributions from redshift-space distortions which typically dominate the result.
• Taking into account the effects of telescope beams and foreground cleaning, we estimate the signal to noise and show that the bispectrum is detectable by both SKA in single-dish mode and HIRAX in interferometer mode, especially at the lower redshifts in their respective ranges.