Lourence Malan
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View article: Exploring One-point Statistics in HERA Phase I Data: Effects of Foregrounds and Systematics on Measuring One-point Statistics
Exploring One-point Statistics in HERA Phase I Data: Effects of Foregrounds and Systematics on Measuring One-point Statistics Open
Measuring one-point statistics in redshifted 21 cm intensity maps offers an opportunity to explore non-Gaussian features of the early Universe. We assess the impact of instrumental effects on measurements made with the Hydrogen Epoch of Re…
View article: Investigating mutual coupling in the hydrogen epoch of reionization array and mitigating its effects on the 21-cm power spectrum
Investigating mutual coupling in the hydrogen epoch of reionization array and mitigating its effects on the 21-cm power spectrum Open
Interferometric experiments designed to detect the highly redshifted 21-cm signal from neutral hydrogen are producing increasingly stringent constraints on the 21-cm power spectrum, but some k-modes remain systematics-dominated. Mutual cou…
View article: Impacts and Statistical Mitigation of Missing Data on the 21 cm Power Spectrum: A Case Study with the Hydrogen Epoch of Reionization Array
Impacts and Statistical Mitigation of Missing Data on the 21 cm Power Spectrum: A Case Study with the Hydrogen Epoch of Reionization Array Open
The precise characterization and mitigation of systematic effects is one of the biggest roadblocks impeding the detection of the fluctuations of cosmological 21 cm signals. Missing data in radio cosmological experiments, often due to radio…
View article: <tt>matvis</tt>: a matrix-based visibility simulator for fast forward modelling of many-element 21 cm arrays
matvis: a matrix-based visibility simulator for fast forward modelling of many-element 21 cm arrays Open
Detection of the faint 21 cm line emission from the Cosmic Dawn and Epoch of Reionization will require not only exquisite control over instrumental calibration and systematics to achieve the necessary dynamic range of observations but also…
View article: A demonstration of the effect of fringe-rate filtering in the hydrogen epoch of reionization array delay power spectrum pipeline
A demonstration of the effect of fringe-rate filtering in the hydrogen epoch of reionization array delay power spectrum pipeline Open
Radio interferometers targeting the 21cm brightness temperature fluctuations at high redshift are subject to systematic effects that operate over a range of different time-scales. These can be isolated by designing appropriate Fourier filt…
View article: Mitigating calibration errors from mutual coupling with time-domain filtering of 21 cm cosmological radio observations
Mitigating calibration errors from mutual coupling with time-domain filtering of 21 cm cosmological radio observations Open
The 21 cm transition from neutral Hydrogen promises to be the best observational probe of the Epoch of Reionization (EoR). This has led to the construction of low-frequency radio interferometric arrays, such as the Hydrogen Epoch of Reioni…
View article: Bayesian estimation of cross-coupling and reflection systematics in 21cm array visibility data
Bayesian estimation of cross-coupling and reflection systematics in 21cm array visibility data Open
Observations with radio arrays that target the 21-cm signal originating from the early Universe suffer from a variety of systematic effects. An important class of these are reflections and spurious couplings between antennas. We apply a Ha…
View article: Direct Optimal Mapping Image Power Spectrum and its Window Functions
Direct Optimal Mapping Image Power Spectrum and its Window Functions Open
The key to detecting neutral hydrogen during the epoch of reionization (EoR) is to separate the cosmological signal from the dominating foreground radiation. We developed direct optimal mapping (DOM) to map interferometric visibilities; it…
View article: Mitigating calibration errors from mutual coupling with time-domain filtering of 21 cm cosmological radio observations
Mitigating calibration errors from mutual coupling with time-domain filtering of 21 cm cosmological radio observations Open
The 21 cm transition from neutral Hydrogen promises to be the best observational probe of the Epoch of Reionisation (EoR). This has led to the construction of low-frequency radio interferometric arrays, such as the Hydrogen Epoch of Reioni…
View article: Investigating Mutual Coupling in the Hydrogen Epoch of Reionization Array and Mitigating its Effects on the 21-cm Power Spectrum
Investigating Mutual Coupling in the Hydrogen Epoch of Reionization Array and Mitigating its Effects on the 21-cm Power Spectrum Open
Interferometric experiments designed to detect the highly redshifted 21-cm signal from neutral hydrogen are producing increasingly stringent constraints on the 21-cm power spectrum, but some k-modes remain systematics-dominated. Mutual cou…
View article: Hydrogen Epoch of Reionization Array (HERA) Phase II Deployment and Commissioning
Hydrogen Epoch of Reionization Array (HERA) Phase II Deployment and Commissioning Open
This paper presents the design and deployment of the Hydrogen Epoch of Reionization Array (HERA) phase II system. HERA is designed as a staged experiment targeting 21 cm emission measurements of the Epoch of Reionization. First results fro…
View article: A demonstration of the effect of fringe-rate filtering in the Hydrogen Epoch of Reionization Array delay power spectrum pipeline
A demonstration of the effect of fringe-rate filtering in the Hydrogen Epoch of Reionization Array delay power spectrum pipeline Open
Radio interferometers targeting the 21cm brightness temperature fluctuations at high redshift are subject to systematic effects that operate over a range of different timescales. These can be isolated by designing appropriate Fourier filte…
View article: Hydrogen Epoch of Reionization Array (HERA) Phase II Deployment and Commissioning
Hydrogen Epoch of Reionization Array (HERA) Phase II Deployment and Commissioning Open
This paper presents the design and deployment of the Hydrogen Epoch of Reionization Array (HERA) phase II system. HERA is designed as a staged experiment targeting 21 cm emission measurements of the Epoch of Reionization. First results fro…
View article: matvis: A matrix-based visibility simulator for fast forward modelling of many-element 21 cm arrays
matvis: A matrix-based visibility simulator for fast forward modelling of many-element 21 cm arrays Open
Detection of the faint 21 cm line emission from the Cosmic Dawn and Epoch of Reionisation will require not only exquisite control over instrumental calibration and systematics to achieve the necessary dynamic range of observations but also…
View article: Bayesian estimation of cross-coupling and reflection systematics in 21cm array visibility data
Bayesian estimation of cross-coupling and reflection systematics in 21cm array visibility data Open
Observations with radio arrays that target the 21-cm signal originating from the early Universe suffer from a variety of systematic effects. An important class of these are reflections and spurious couplings between antennas. We apply a Ha…
View article: Direct Optimal Mapping Image Power Spectrum and its Window Functions
Direct Optimal Mapping Image Power Spectrum and its Window Functions Open
The key to detecting neutral hydrogen during the epoch of reionization (EoR) is to separate the cosmological signal from the dominating foreground radiation. We developed direct optimal mapping (DOM) to map interferometric visibilities; it…
View article: Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations
Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations Open
We report the most sensitive upper limits to date on the 21 cm epoch of reionization power spectrum using 94 nights of observing with Phase I of the Hydrogen Epoch of Reionization Array (HERA). Using similar analysis techniques as in previ…
View article: Search for the Epoch of Reionization with HERA: upper limits on the closure phase delay power spectrum
Search for the Epoch of Reionization with HERA: upper limits on the closure phase delay power spectrum Open
Radio interferometers aiming to measure the power spectrum of the redshifted 21 cm line during the Epoch of Reionization (EoR) need to achieve an unprecedented dynamic range to separate the weak signal from overwhelming foreground emission…
View article: Characterization of inpaint residuals in interferometric measurements of the epoch of reionization
Characterization of inpaint residuals in interferometric measurements of the epoch of reionization Open
To mitigate the effects of Radio Frequency Interference (RFI) on the data analysis pipelines of 21 cm interferometric instruments, numerous inpaint techniques have been developed. In this paper, we examine the qualitative and quantitative …
View article: Impact of instrument and data characteristics in the interferometric reconstruction of the 21 cm power spectrum
Impact of instrument and data characteristics in the interferometric reconstruction of the 21 cm power spectrum Open
Combining the visibilities measured by an interferometer to form a cosmological power spectrum is a complicated process. In a delay-based analysis, the mapping between instrumental and cosmological space is not a one-to-one relation. Inste…
View article: Bayesian jackknife tests with a small number of subsets: application to HERA 21 cm power spectrum upper limits
Bayesian jackknife tests with a small number of subsets: application to HERA 21 cm power spectrum upper limits Open
We present a Bayesian jackknife test for assessing the probability that a data set contains biased subsets, and, if so, which of the subsets are likely to be biased. The test can be used to assess the presence and likely source of statisti…
View article: Characterization Of Inpaint Residuals In Interferometric Measurements of the Epoch Of Reionization
Characterization Of Inpaint Residuals In Interferometric Measurements of the Epoch Of Reionization Open
Radio Frequency Interference (RFI) is one of the systematic challenges preventing 21cm interferometric instruments from detecting the Epoch of Reionization. To mitigate the effects of RFI on data analysis pipelines, numerous inpaint techni…
View article: Impact of instrument and data characteristics in the interferometric reconstruction of the 21 cm power spectrum
Impact of instrument and data characteristics in the interferometric reconstruction of the 21 cm power spectrum Open
Combining the visibilities measured by an interferometer to form a cosmological power spectrum is a complicated process. In a delay-based analysis, the mapping between instrumental and cosmological space is not a one-to-one relation. Inste…
View article: Direct Optimal Mapping for 21 cm Cosmology: A Demonstration with the Hydrogen Epoch of Reionization Array
Direct Optimal Mapping for 21 cm Cosmology: A Demonstration with the Hydrogen Epoch of Reionization Array Open
Motivated by the desire for wide-field images with well-defined statistical properties for 21 cm cosmology, we implement an optimal mapping pipeline that computes a maximum likelihood estimator for the sky using the interferometric measure…
View article: Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations
Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations Open
We report the most sensitive upper limits to date on the 21 cm epoch of reionization power spectrum using 94 nights of observing with Phase I of the Hydrogen Epoch of Reionization Array (HERA). Using similar analysis techniques as in previ…
View article: First Results from HERA Phase I: Upper Limits on the Epoch of Reionization 21 cm Power Spectrum
First Results from HERA Phase I: Upper Limits on the Epoch of Reionization 21 cm Power Spectrum Open
We report upper limits on the Epoch of Reionization 21 cm power spectrum at redshifts 7.9 and 10.4 with 18 nights of data (∼36 hr of integration) from Phase I of the Hydrogen Epoch of Reionization Array (HERA). The Phase I data show eviden…
View article: Validation of the HERA Phase I Epoch of Reionization 21 cm Power Spectrum Software Pipeline
Validation of the HERA Phase I Epoch of Reionization 21 cm Power Spectrum Software Pipeline Open
We describe the validation of the HERA Phase I software pipeline by a series of modular tests, building up to an end-to-end simulation. The philosophy of this approach is to validate the software and algorithms used in the Phase I upper-li…
View article: HERA Phase I Limits on the Cosmic 21 cm Signal: Constraints on Astrophysics and Cosmology during the Epoch of Reionization
HERA Phase I Limits on the Cosmic 21 cm Signal: Constraints on Astrophysics and Cosmology during the Epoch of Reionization Open
Recently, the Hydrogen Epoch of Reionization Array (HERA) has produced the experiment’s first upper limits on the power spectrum of 21 cm fluctuations at z ∼ 8 and 10. Here, we use several independent theoretical models to infer constraint…
View article: Automated Detection of Antenna Malfunctions in Large‐ <i>N</i> Interferometers: A Case Study With the Hydrogen Epoch of Reionization Array
Automated Detection of Antenna Malfunctions in Large‐ <i>N</i> Interferometers: A Case Study With the Hydrogen Epoch of Reionization Array Open
We present a framework for identifying and flagging malfunctioning antennas in large radio interferometers. We outline two distinct categories of metrics designed to detect outliers along known failure modes of large arrays: cross‐correlat…
View article: Effects of model incompleteness on the drift-scan calibration of radio telescopes
Effects of model incompleteness on the drift-scan calibration of radio telescopes Open
Precision calibration poses challenges to experiments probing the redshifted 21-cm signal of neutral hydrogen from the Cosmic Dawn and Epoch of Reionization (z ∼ 30–6). In both interferometric and global signal experiments, systematic cali…