Strategy for mitigation of systematics for EoR experiments with the Murchison Widefield Array

TL;DR

This paper presents a systematic mitigation strategy for foreground and instrumental systematics in 21 cm Epoch of Reionisation experiments using the Murchison Widefield Array, improving data quality for cosmological signal detection.

Contribution

It introduces a statistical framework for identifying and filtering systematic effects in MWA data, selecting cleaner observations for EoR analysis.

Findings

Selected 18% of observations with fewer systematics

Reduced systematic effects increase confidence in 21 cm measurements

Implemented filters effectively mitigate calibration and RFI-related errors

Abstract

Observations of the 21 cm signal face significant challenges due to bright astrophysical foregrounds that are several orders of magnitude higher than the brightness of the hydrogen line, along with various systematics. Successful 21 cm experiments require accurate calibration and foreground mitigation. Errors introduced during the calibration process such as systematics, can disrupt the intrinsic frequency smoothness of the foregrounds, leading to power leakage into the Epoch of Reionisation (EoR) window. Therefore, it is essential to develop strategies to effectively address these challenges. In this work, we adopt a stringent approach to identify and address suspected systematics, including malfunctioning antennas, frequency channels corrupted by radio frequency interference (RFI), and other dominant effects. We implement a statistical framework that utilises various data products from the data processing pipeline to derive specific criteria and filters. These criteria and filters are applied at intermediate stages to mitigate systematic propagation from the early stages of data processing. Our analysis focuses on observations from the Murchison Widefield Array (MWA) Phase I configuration. Out of the observations processed by the pipeline, our approach selects 18%, totalling 58 hours, that exhibit fewer systematic effects. The successful selection of observations with reduced systematic dominance enhances our confidence in achieving 21 cm measurements.