Tuesday

The redshifted 21-cm signal, originating from the neutral hydrogen (HI) during the epoch of reionization (EoR) is expected to be highly non-Gaussian in nature due to the morphology of the HI distribution during this period. The first generation of the low frequency radio interferometers (GMRT, LOFAR, PAPER etc) aim to detect this signal through it´s power spectrum, owing to a higher signal-to-noise ratio (SNR) for this estimator. However, the power spectrum will not be able to capture the intrinsic non-Gaussianity of the signal and thus will also not be able to break the degeneracy between the different signal parameters. We propose the use of a higher order estimator-- the bispectrum (Fourier equivalent of the three point correlation function)-- to quantify this signal, which is also expected to capture it´s non-Gaussian character.
Using a set of semi-numerical simulations for the signal, we try to find out the optimal closed triangle configuration in the wave number (or k) space for the bispectrum estimation, that is sensitive to the important characteristics of the signal. We also provide a simple physical model to interpret the behaviour of the EoR 21-cm bispectrum and its evolution with the changing state of ionization of the universe.