New EoR Power Spectrum Limits From MWA Phase II Using the Delay Spectrum Method and Novel Systematic Rejection

Q: What dataset and analysis pipeline are used to derive the new EoR power spectrum limits?

The limits are obtained from MWA Phase II data using the simpleDS delay spectrum pipeline.

Q: How does this work relate to earlier studies on the same observations?

Prior analyses used a reconstructed-sky estimator (FHD/ǧppsilon), while this study applies a measured-sky approach to the same dataset, focusing on different baseline subsets.

Q: Why is mitigating a common-mode systematic crucial in this analysis?

A previously unrecognized common-mode systematic can introduce an overall negative bias; if untreated, it can cause foreground-contaminated results to look like stringent, noise-limited constraints.

Aug 22, 2026

Uploaded by WPS_1786070896

Analysis presents Epoch of Reionization constraints derived from Phase II observations of the Murchison Widefield Array using the simpleDS delay spectrum pipeline. The study extends prior work by applying a measured-sky approach alongside reconstructed-sky estimators to the same dataset, enabling direct comparison across 21 cm power spectrum estimation methods. Reported limits cover 21 cm power spectrum amplitude over a broad |Δ²| range, with the tightest measurement at Δ²≤4.58×103 mK² near k=0.190 h100Mpc−1. Achieving these limits requires mitigation of a previously unidentified common-mode systematic that, if ignored, can bias results and make foreground-contaminated measurements appear overly stringent.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages20

Reading Time50 min

AccessFree to download

Abstract

Introduction

Instrumentation and observational goal

Estimator classes and prior work

Measured-sky analysis and baseline selection

Common-mode systematic and its impact

arXiv :2210 . 10885v2 [ astro-ph .CO] 4 Apr 2023 New EoR Power Spectrum Limits From MWA Phase II Using the Delay Spectrum Method and Novel Systematic Rejection Matthew Kolopanis 1★ , Jonathan C. Pober2 , Daniel C. Jacobs 1 , Samantha McGraw2 1 School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA 2 Department of Physics, Brown University, Providence, RI, USA Accepted XXX. Received YYY; in original form ZZZ ABSTRACT We present an analysis of Epoch of Reionization data from Phase II of the Murchison Wideﬁeld Array using the simpleDS delay spectrum pipeline. Prior work analyzed the same observations using the FHD/􀁙ppsilon imaging pipeline, and so the present analysis represents the ﬁrst time that both principal types of 21 cm cosmology power spectrum estimation approaches have been applied to the same data set. Our limits on the 21 cm power spectrum amplitude span a range in 􀀺 space of | 􀀺 | < 1 ℎ 100Mpc−1 with a lowest measurement of Δ2 ( 􀀺) ≤ 4.58 × 103 mK2 at 􀀺 = 0. 190 ℎ100Mpc−1 and 􀁉 = 7. 14. In order to achieve these limits, we need to mitigate a previously unidentiﬁed common mode systematic in the data set. If not accounted for, this systematic introduces an overall negative bias that can make foreground contaminated measurements appear as stringent, noise-limited constraints on the 21 cm signal amplitude. The identiﬁcation of this systematic highlights the risk in modeling systematics as positive-deﬁnite contributions to the power spectrum and in “conservatively” interpreting all measurements as upper limits. Key words: dark ages, reionization, ﬁrst stars – techniques: interferometric – methods: data analysis 1 INTRODUCTION Detecting the highly-redshifted 21 cm signal from neutral hydrogen is a major goal of modern cosmology. Multiple experiments targeting such a detection are now either complete or underway, including The Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER; Parsons et al. 2010; Kolopanis et al. 2019), the Giant Metrewave Radio Telescope (GMRT; Swarup et al. 1991; Paciga et al. 2013), the Low-Frequency Array (LOFAR; van Haarlem et al. 2013; Mertens et al. 2020), the Hydrogen Epoch of Reionization Array (HERA; DeBoer et al. 2017; HERA Collaboration et al. 2022b), and the Murchison Wideﬁeld Array (MWA; Tingay et al. 2013; Wayth et al. 2018; Trott et al. 2020), all of which are radio interferometers with the aim of measuring the power spectrum of spatial ﬂuctuations in the hydrogen signal during the cosmological Epoch of Reionization.1 The 21 cm signal must be separated from extremely bright foreground emission based on the distinct spectral behavior of the two emission mechanisms (spectrally structured for the 21 cm signal and smooth for the foregrounds) . Teams from each experiment have developed a number of techniques to enable the extraction of the 21 cm signal, including novel approaches to calibration, systematic mitigation, and power spectrum estimation. Morales et al. (2019) show that, despite the intricacies of each approach, techniques used for power spectrum (PS) estimation can ★ [E-mail: Matthew.Kolopanis@asu.edu](E-mail: Matthew.Kolopanis@asu.edu) 1 Many other approaches for pursuing this signal exist, including measurements of the sky-averaged “global" signal (e.g. Bowman et al. 2018) and measurements aimed at other redshifts (e.g. Eastwood et al. 2019) . largely be classiﬁed into two categories: “reconstructed sky” estimators, which attempt to correct for the response of the radio interferometer to recover the power spectrum of the “true” sky, and “measured sky” estimators, which make no correction for the telescope response and instead recover the power spectrum of the sky “as seen” by the telescope. Through simulations, Morales et al. (2019) demonstrate the signature of foreground contamination in the measured power spectra are distinct for these two classes of estimators. Moreover, they describe how errors in th

FAQs

What dataset and analysis pipeline are used to derive the new EoR power spectrum limits?

The limits are obtained from MWA Phase II data using the simpleDS delay spectrum pipeline.

How does this work relate to earlier studies on the same observations?

Prior analyses used a reconstructed-sky estimator (FHD/ǧppsilon), while this study applies a measured-sky approach to the same dataset, focusing on different baseline subsets.

Why is mitigating a common-mode systematic crucial in this analysis?

A previously unrecognized common-mode systematic can introduce an overall negative bias; if untreated, it can cause foreground-contaminated results to look like stringent, noise-limited constraints.

Aug 22, 2026

Uploaded by WPS_1786070896