The H i intensity mapping bispectrum including observational effects

Abstract

ABSTRACT The bispectrum is a three-point statistic with the potential to provide additional information beyond power spectra analyses of survey data sets. Radio telescopes that broadly survey the 21-cm emission from neutral hydrogen (H i) are a promising way to probe LSS and in this work we present an investigation into the H i intensity mapping (IM) bispectrum using simulations. We present a model of the redshift space H i IM bispectrum including observational effects from the radio telescope beam and 21-cm foreground contamination. We validate our modelling prescriptions with measurements from robust IM simulations, inclusive of these observational effects. Our foreground simulations include polarization leakage, on which we use a principal component analysis cleaning method. We also investigate the effects from a non-Gaussian beam including side-lobes. For a MeerKAT-like single-dish IM survey at z = 0.39, we find that foreground removal causes an $8{{\ \rm per\ cent}}$ reduction in the equilateral bispectrum’s signal-to-noise ratio, whereas the beam reduces it by $62{{\ \rm per\ cent}}$. We find our models perform well, generally providing $\chi ^2_\text{dof}\sim 1$, indicating a good fit to the data. Whilst our focus is on post-reionization, single-dish IM, our modelling of observational effects, especially foreground removal, can also be relevant to interferometers and reionization studies.