Aliasing from Galactic Plane Setting in Widefield Radio Interferometry

TL;DR

This paper investigates how the setting of the Galactic plane affects aliasing in widefield radio interferometry, demonstrating that even minimal beam attenuation may be insufficient for precision science, and showing that aliasing removal improves data Gaussianity.

Contribution

It provides the first detailed all-sky simulations of Galactic plane setting effects and evaluates their impact on the Murchison Widefield Array's data quality and scientific analyses.

Findings

Galactic plane setting enhances aliasing effects in radio interferometry.

Minimal beam attenuation (0.1%) may not suffice for high-precision measurements.

Aliasing removal leads to more Gaussian noise statistics in residual images.

Abstract

Measurements with widefield radio interferometers often include the near-infinite gradient between the sky and the horizon. This causes aliasing inherent to the measurement itself, and is purely a consequence of the Fourier basis. For this reason, the horizon is often attenuated by the instrumental beam down to levels deemed inconsequential. However, this effect is enhanced via our own Galactic plane as it sets over the course of a night. We show all-sky simulations of the Galactic plane setting in a radio interferometer in detail for the first time. We then apply these simulations to the Murchison Widefield Array to show that a beam attenuation of 0.1% is not sufficient in some precision science cases. We determine that the noise statistics of the residual data image are drastically more Gaussian with aliasing removal, and explore consequences in simulation for cataloging of extragalactic sources and 21 cm Epoch of Reionization detection via the power spectrum.