Speaker
Description
While the detection of the power spectrum has been the primary goal of 21 cm observations, it does not tell us the whole story of the Epoch of Reionization (EoR). Bispectrum, the next higher-order statistic, can access the additional information on non-Gaussianity, mode coupling, and topology of HI distribution during the EoR. Observationally, the bispectrum can be computed from radio-interferometric data by correlating the 3-visibilities (https://arxiv.org/abs/2506.10526). I will talk about our recent efforts to measure the bispectrum using the drift scan MWA observations at z = 8.2 (https://arxiv.org/abs/2507.04964). A significant contribution of this work is to characterize the behavior of foregrounds and the identification of the 'foreground wedge' feature in the cylindrical bispectrum, analogous to the case of the power spectrum. We have performed the comprehensive study considering all possible triangle configurations and placed the preliminary upper limits on the EoR 21 cm bispectrum signal. I will talk on (i) why we need to go beyond 2-point statistics (ii) how to compute the bispectrum directly from radio-interferometric visibility data in an efficient way (iii) how the bispectrum of astrophysical foregrounds looks like (iv) current upper limits on the EoR bispectrum (v) lessons learned for the EoR bispectrum detection - the goal which aligns with the capabilities of the SKA.
