Improving the Epoch of Reionization Power Spectrum Results from Murchison Widefield Array Season 1 Observations

TL;DR

This paper improves the measurement precision of the 21 cm Epoch of Reionization power spectrum using MWA data by implementing advanced systematics mitigation and RFI excision, resulting in significantly tighter upper limits.

Contribution

The study introduces new analysis techniques and RFI mitigation methods that reduce systematics and improve the upper limits on EoR power spectrum measurements.

Findings

Lowered analysis systematics by a factor of 2.8

Further reduced systematics by a factor of 3.8 through RFI excision

Achieved an order of magnitude improvement in EoR power spectrum upper limits

Abstract

Measurements of 21 cm Epoch of Reionization (EoR) structure are subject to systematics originating from both the analysis and the observation conditions. Using 2013 data from the Murchison Widefield Array (MWA), we show the importance of mitigating both sources of contamination. A direct comparison between results from Beardsley et al. 2016 and our updated analysis demonstrates new precision techniques, lowering analysis systematics by a factor of 2.8 in power. We then further lower systematics by excising observations contaminated by ultra-faint RFI, reducing by an additional factor of 3.8 in power for the zenith pointing. With this enhanced analysis precision and newly developed RFI mitigation, we calculate a noise-dominated upper limit on the EoR structure of $\Delta^2 \leq 3.9 \times 10^3$ mK$^2$ at $k=0.20$ $\textit{h}$ Mpc$^{-1}$ and $z=7$ using 21 hr of data, improving previous MWA limits by almost an order of magnitude.