Evidence of Ultra-faint Radio Frequency Interference in Deep 21~cm Epoch of Reionization Power Spectra with the Murchison Widefield Array

Abstract

We present deep upper limits from the 2014 Murchison Widefield Array (MWA) Phase I observing season, with a particular emphasis on identifying the spectral fingerprints of extremely faint radio frequency interference (RFI) contamination in the 21~cm power spectra (PS). After meticulous RFI excision involving a combination of the \textsc{SSINS} RFI flagger and a series of PS-based jackknife tests, our lowest upper limit on the Epoch of Reionization (EoR) 21~cm PS signal is ${\Delta }^2\le 1.61\cdot 10^4{\text{ mK}}^2$ at $k=0.258{\text{ h Mpc}}^{-1}$ at a redshift of 6.5 using 14.7 hours of data. By leveraging our understanding of how even fainter RFI is likely to contaminate the EoR PS, we are able to identify ultra-faint RFI signals in the cylindrical PS. Surprisingly this signature is most obvious in PS formed with less than an hour of data, but is potentially subdominant to other systematics in multiple-hour integrations. Since the total RFI budget in a PS detection is quite strict, this nontrivial integration behavior suggests a need to more realistically model coherently integrated ultra-faint RFI in PS measurements so that its potential contribution to a future detection can be diagnosed.

Update deeepest limit redshift based on erratum

References in corpus (33)

• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey I: A low-frequency extragalactic catalogue
• Improved upper limits on the 21-cm signal power spectrum of neutral hydrogen at $\mathbf{z}\approx 9.1$ from LOFAR
• The Epoch of Reionization Window: I. Mathematical Formalism
• 21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal
• Deep multi-redshift limits on Epoch of Reionisation 21cm Power Spectra from Four Seasons of Murchison Widefield Array Observations
• The Epoch of Reionization Window: II. Statistical Methods for Foreground Wedge Reduction
• First Results from HERA Phase I: Upper Limits on the Epoch of Reionization 21 cm Power Spectrum
• Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations
• Real-Time Calibration of the Murchison Widefield Array
• First Season MWA EoR Power Spectrum Results at Redshift 7
• The low-frequency environment of the Murchison Widefield Array: radio-frequency interference analysis and mitigation
• Improving the Epoch of Reionization Power Spectrum Results from Murchison Widefield Array Season 1 Observations
• Fast Holographic Deconvolution: a new technique for precision radio interferometry
• First Season MWA Phase II EoR Power Spectrum Results at Redshift 7
• Characterisation of the ionosphere above the Murchison Radio Observatory using the Murchison Widefield Array
• Mitigating Internal Instrument Coupling II: A Method Demonstration with the Hydrogen Epoch of Reionization Array
• Mitigating Internal Instrument Coupling for 21 cm Cosmology I: Temporal and Spectral Modeling in Simulations
• The impact of interference excision on 21-cm Epoch of Reionization power spectrum analyses
• Redundant-Baseline Calibration of the Hydrogen Epoch of Reionization Array
• The FHD/$\mathbf{\epsilon }$ppsilon Epoch of Reionization Power Spectrum Pipeline
• DAYENU: A Simple Filter of Smooth Foregrounds for Intensity Mapping Power Spectra
• Radio emission from negative lightning leader steps reveals inner meter-scale structure
• A Unified Calibration Framework for 21 cm Cosmology
• Quantifying Excess Power from Radio Frequency Interference in Epoch of Reionization Measurements
• A Digital-Receiver for the Murchison Widefield Array
• A survey of spatially and temporally resolved radio frequency interference in the FM band at the Murchison Radio-astronomy Observatory
• Interferometric imaging of Intensely Radiating Negative Leaders
• Exploring the consequences of chromatic data excision in 21-cm Epoch of Reionization power spectrum observations
• Improved Sensitivity for Space Domain Awareness Observations with the Murchison Widefield Array
• MWA tied-array processing III: Microsecond time resolution via a polyphase synthesis filter
• A Low Frequency Blind Survey of the Low Earth Orbit Environment using Non-Coherent Passive Radar with the Murchison Widefield Array
• Why and When to Expect Gaussian Error Distributions in Epoch of Reionization 21-cm Power Spectrum Measurements

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