The Murchison Widefield Array 21 cm Power Spectrum Analysis Methodology

TL;DR

This paper details the methodology for analyzing the 21 cm power spectrum from the Murchison Widefield Array, comparing multiple pipelines to validate cosmological hydrogen signals during reionization.

Contribution

It introduces a comprehensive comparison of independent data calibration and reduction pipelines, highlighting their tradeoffs and emphasizing the importance of reproducibility in 21 cm cosmology analysis.

Findings

Different pipelines produce power spectra with varying tradeoffs.

Reproducibility issues are significant and can affect results.

Lessons learned improve future analysis robustness.

Abstract

We present the 21 cm power spectrum analysis approach of the Murchison Widefield Array Epoch of Reionization project. In this paper, we compare the outputs of multiple pipelines for the purpose of validating statistical limits cosmological hydrogen at redshifts between 6 and 12. Multiple, independent, data calibration and reduction pipelines are used to make power spectrum limits on a fiducial night of data. Comparing the outputs of imaging and power spectrum stages highlights differences in calibration, foreground subtraction and power spectrum calculation. The power spectra found using these different methods span a space defined by the various tradeoffs between speed, accuracy, and systematic control. Lessons learned from comparing the pipelines range from the algorithmic to the prosaically mundane; all demonstrate the many pitfalls of neglecting reproducibility. We briefly discuss the way these different methods attempt to handle the question of evaluating a significant detection in the presence of foregrounds.