Revisiting the theory of interferometric wide-field synthesis

TL;DR

This paper introduces a novel formalism for wide-field interferometric imaging in radioastronomy, offering advantages in processing short spacings, data storage, and computational efficiency over traditional mosaicking methods.

Contribution

It proposes a new wide-field synthesis approach that differs from standard mosaicking, explicitly synthesizing visibilities at finer spatial resolutions and efficiently handling heterogeneous arrays and short spacings.

Findings

The new method recovers sky brightness similarly to mosaicking.

It processes short spacings from single-dish and heterogeneous arrays.

It potentially reduces data storage and computational costs.

Abstract

After several generations of interferometers in radioastronomy, wide-field imaging at high angular resolution is today a major goal for trying to match optical wide-field performances. All the radio-interferometric, wide-field imaging methods currently belong to the mosaicking family. Based on a 30 years old, original idea from Ekers & Rots, we aim at proposing an alternate formalism. Starting from their ideal case, we successively evaluate the impact of the standard ingredients of interferometric imaging. A comparison with standard nonlinear mosaicking shows that both processing schemes are not mathematically equivalent, though they both recover the sky brightness. In particular, the weighting scheme is very different in both methods. Moreover, the proposed scheme naturally processes the short spacings from both single-dish antennas and heterogeneous arrays. Finally, the sky gridding of the measured visibilities, required by the proposed scheme, may potentially save large amounts of hard-disk space and cpu processing power over mosaicking when handling data sets acquired with the on-the-fly observing mode. We propose to call this promising family of imaging methods wide-field synthesis because it explicitly synthesizes visibilities at a much finer spatial frequency resolution than the one set by the diameter of the interferometer antennas.