A visibility-based angular bispectrum estimator for radio-interferometric data

Abstract

Considering radio-interferometric observations, we present a fast and efficient estimator to compute the binned angular bispectrum (ABS) from gridded visibility data. The estimator makes use of Fast Fourier Transform (FFT) techniques to compute the bispectrum covering all possible triangle shapes and sizes. Here, we present the formalism of the estimator and validate it using simulated visibility data for the Murchison Widefield Array (MWA) observations at $\nu=154.25$ MHz. We find that our estimator is able to faithfully recover the ABS of the simulated sky signal with $\approx 10\%-15 \%$ accuracy for a wide variety of triangle shapes and sizes across the range of angular multipoles $46 \le \ell \le 1320$. In future work, we plan to apply this to actual data and also generalize it to estimate the three-dimensional redshifted 21-cm bispectrum.