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

TL;DR

This paper introduces a fast, FFT-based estimator for the angular bispectrum from radio-interferometric data, validated with simulations, enabling efficient analysis of sky signals for current and future 21-cm cosmology studies.

Contribution

It presents a novel, computationally efficient bispectrum estimator tailored for radio interferometry data, validated with simulations, and adaptable for future 3D redshifted 21-cm bispectrum analysis.

Findings

Estimator recovers bispectrum with 10-15% accuracy across various triangle configurations.

Validated using simulated MWA data at 154.25 MHz.

Effective for angular multipoles 46 to 1320.

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.