High Resolution, Wide Field, Narrow Band, Snapshot Imaging

TL;DR

This paper analyzes the imaging performance of interferometric arrays for high resolution, wide field, narrow band snapshot imaging, revealing how uv-cell sizing and weighting schemes affect image quality and noise correlation.

Contribution

It demonstrates that small uv-cell sizes enable effective gridding for dense arrays and explores the implications of weighting schemes on image noise and resolution.

Findings

Uniform weighting approximates Natural weighting in dense arrays.

Image noise is highly correlated on scales of core baselines.

Core antennas can be used as a separate subarray for low resolution science.

Abstract

We investigate the imaging performance of an interferometric array in the case of wide field, high resolution, narrow band, snapshot imaging. We find that, when uv-cell sizes are sufficiently small (ie. image sizes are sufficiently large), each instantaneous visibility record is gridded into its own uv-cell. This holds even for dense arrays, like the core of the next generation VLA. In this particular, application, Uniform weighting of the gridded visibilities approaches Natural weighting, with its often deleterious consequences on the resulting synthesized beam. For a core-dominated array, we show that the resulting image noise is highly correlated on scales comparable to the spatial frequencies of the core baselines. In general, this study accentuates the fact that, for imaging applications that require high resolution (Plains array and greater), many of the core antennas can be employed as a separate subarray for low resolution science, without sacrificing the quality of the high resolution science.