Correcting the Polarization Leakage Phases and Amplitudes Throughout the Primary Beam of an Interferometer

TL;DR

This paper introduces a method to measure and correct wide-field polarization leakage in heterogeneous interferometric arrays, improving the accuracy of polarimetric imaging by accounting for baseline-dependent effects and antenna beam patterns.

Contribution

It presents a novel technique to accurately measure and remove polarization leakage across the primary beam of heterogeneous arrays, including mapping antenna voltage patterns.

Findings

Effective correction of polarization leakage demonstrated.

Improved accuracy in Stokes parameter imaging.

Method accounts for array heterogeneities and baseline dependence.

Abstract

Polarimetric observations are affected by leakage of unpolarized light into the polarization channels, in a way that varies with the angular position of the source relative to the optical axis. The off-axis part of the leakage is often corrected by subtracting from each polarization image the product of the unpolarized map and a leakage map, but it is seldom realized that heterogeneities in the array shift the loci of the leaked radiation in a baseline-dependent fashion. We present here a method to measure and remove the wide-field polarization leakage of a heterogeneous array. The process also maps the complex voltage patterns of each antenna, which can be used to correct all Stokes parameters for imaging errors due to the primary beams.