First Season MWA Phase II EoR Power Spectrum Results at Redshift 7

TL;DR

This paper presents new upper limits on the 21cm EoR power spectrum at redshifts around 7, using 40 hours of MWA Phase II data with improved calibration and analysis techniques.

Contribution

It introduces advanced calibration and data quality methods for EoR power spectrum analysis, achieving tighter constraints with MWA Phase II data.

Findings

Set new upper limits on the EoR power spectrum at z~7.

Achieved sensitivity in the range 0.18 to 1.6 h Mpc^{-1}.

Lowest measurement of Δ^2 ≤ 2.39×10^3 mK^2 at k=0.59 h Mpc^{-1}.

Abstract

The compact configuration of Phase II of the Murchison Widefield Array (MWA) consists of both a redundant subarray and pseudo-random baselines, offering unique opportunities to perform sky-model and redundant interferometric calibration. The highly redundant hexagonal cores give improved power spectrum sensitivity. In this paper, we present the analysis of nearly 40 hours of data targeting one of the MWA's EoR fields observed in 2016. We use both improved analysis techniques presented in Barry et al. (2019) as well as several additional techniques developed for this work, including data quality control methods and interferometric calibration approaches. We show the EoR power spectrum limits at redshift 6.5, 6.8 and 7.1 based on our deep analysis on this 40-hour data set. These limits span a range in $k$ space of $0.18$ $h$ $\mathrm{Mpc^{-1}}$ $<k<1.6$ $h$ $\mathrm{Mpc^{-1}}$, with a lowest measurement of $\Delta^2\leqslant2.39\times 10^3$ $\mathrm{mK}^2$ at $k=0.59$ $h$ $\mathrm{Mpc^{-1}}$ and $z=6.5$.