Michael J. Wilensky
A5046303240- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Antenna Design and Optimization
- Millimeter-Wave Propagation and Modeling
- Radio Wave Propagation Studies
- Astronomy and Astrophysical Research
- Telecommunications and Broadcasting Technologies
- Astronomical Observations and Instrumentation
- Microwave Engineering and Waveguides
- Particle Accelerators and Free-Electron Lasers
- Galaxies: Formation, Evolution, Phenomena
- Speech and Audio Processing
- Satellite Communication Systems
- Gyrotron and Vacuum Electronics Research
- Electromagnetic Compatibility and Measurements
- Direction-of-Arrival Estimation Techniques
- Advanced Wireless Communication Techniques
- Advanced Multi-Objective Optimization Algorithms
- Calibration and Measurement Techniques
- Genetic factors in colorectal cancer
- History and Developments in Astronomy
- Mathematics and Applications
- Data Quality and Management
- Computational Physics and Python Applications
- Precipitation Measurement and Analysis
University of Manchester
2022-2025
McGill University
2024-2025
Winona State University
2024
Space Science Institute
2024
University of Washington
2019-2023
Queen Mary University of London
2021-2023
We compute the spherically-averaged power spectrum from four seasons of data obtained for Epoch Reionisation (EoR) project observed with Murchison Widefield Array (MWA). measure EoR over $k= 0.07-3.0~h$Mpc$^{-1}$ at redshifts $z=6.5-8.7$. The largest aggregation 110 hours on EoR0 high-band (3,340 observations), yields a lowest measurement (43~mK)$^2$ = 1.8$\times$10$^3$ mK$^2$ $k$=0.14~$h$Mpc$^{-1}$ and $z=6.5$ (2$\sigma$ thermal noise plus sample variance). Using Real-Time System to...
Abstract We report the most sensitive upper limits to date on 21 cm epoch of reionization power spectrum using 94 nights observing with Phase I Hydrogen Epoch Reionization Array (HERA). Using similar analysis techniques as in previously reported limits, we find at 95% confidence that Δ 2 ( k = 0.34 h Mpc −1 ) ≤ 457 mK z 7.9 and 0.36 3496 10.4, an improvement by a factor 2.1 2.6, respectively. These are mostly consistent thermal noise over wide range after our data quality cuts, despite...
Measurements of 21 cm Epoch Reionization (EoR) structure are subject to systematics originating from both the analysis and observation conditions. Using 2013 data Murchison Widefield Array (MWA), we show importance mitigating sources contamination. A direct comparison between results Beardsley et al. 2016 our updated demonstrates new precision techniques, lowering by a factor 2.8 in power. We then further lower excising observations contaminated ultra-faint RFI, reducing an additional 3.8...
Abstract The compact configuration of Phase II the Murchison Widefield Array (MWA) consists both a redundant subarray and pseudo-random baselines, offering unique opportunities to perform sky-model interferometric calibration. highly hexagonal cores give improved power spectrum sensitivity. In this paper, we present analysis nearly 40 hr data targeting one MWA’s epoch reionization (EoR) fields observed in 2016. We use techniques presented Barry et al. several additional developed for work,...
ABSTRACT Observations in the lowest Murchison Widefield Array (MWA) band between 75 and 100 MHz have potential to constrain distribution of neutral hydrogen intergalactic medium at redshift ∼13–17. Using 15 h MWA data, we analyse systematics this such as radio-frequency interference (RFI), ionospheric wide field effects. By updating position point sources, mitigate direction-independent calibration error due offsets. Our strategy is optimized for frequency bands by reducing number...
Abstract Radio interferometers designed to probe the 21 cm signal from Cosmic Dawn and Epoch of Reionization must contend with systematic effects that make it difficult achieve sufficient dynamic range separate foreground emission other effects. For instance, instrument’s chromatic response modulates otherwise spectrally smooth foregrounds, making them model, while a significant fraction data be excised due presence radio-frequency interference, leaving gaps in data. Errors modeling...
Abstract The precise characterization and mitigation of systematic effects is one the biggest roadblocks impeding detection fluctuations cosmological 21 cm signals. Missing data in radio experiments, often due to frequency interference (RFI), pose a particular challenge power spectrum analysis as this could lead ringing bright foreground modes Fourier space, heavily contaminating Here we show that problem missing becomes even more arduous presence effects. Using realistic numerical...
ABSTRACT Detection of the faint 21 cm line emission from Cosmic Dawn and Epoch Reionization will require not only exquisite control over instrumental calibration systematics to achieve necessary dynamic range observations but also validation analysis techniques demonstrate their statistical properties signal loss characteristics. A key ingredient in achieving this is ability perform high-fidelity simulations kinds data that are produced by large, many-element, radio interferometric arrays...
Calibration precision is currently a limiting systematic in 21 cm cosmology experiments. While there are innumerable calibration approaches, most can be categorized as either `sky-based,' relying on an extremely accurate model of astronomical foreground emission, or `redundant,' requiring precisely regular array with near-identical antenna response patterns. Both these classes inflexible to the realities interferometric measurement. In practice, errors model, position offsets, and beam...
Abstract We present deep upper limits from the 2014 Murchison Widefield Array Phase I observing season, with a particular emphasis on identifying spectral fingerprints of extremely faint radio frequency interference (RFI) contamination in 21 cm power spectra (PS). After meticulous RFI excision involving combination SSINS flagger and series PS-based jackknife tests, our lowest limit Epoch Reionization (EoR) PS signal is Δ 2 ≤ 1.61 × 10 4 mK at k = 0.258h Mpc −1 redshift 7.1 using 14.7 hr...
ABSTRACT Power spectrum estimators are an important tool in efforts to detect the 21 cm brightness temperature fluctuations from neutral hydrogen at early times. An initial detection will likely be statistical nature, meaning that it not possible make a coherent map of fluctuations; instead, only their variance measured against background noise and residual systematic effects. Optimal quadratic estimator-based methods often apply inverse covariance weighting data. However, inaccurate...
We introduce a new pipeline for analyzing and mitigating radio frequency interference (RFI), which we call Sky-Subtracted Incoherent Noise Spectra (SSINS). SSINS is designed to identify remove faint RFI below the single baseline thermal noise by employing frequency-matched detection algorithm on baseline-averaged amplitudes of time-differenced visibilities. demonstrate capabilities using Murchison Widefield Array (MWA) in Western Australia. successfully image aircraft flying over array via...
ABSTRACT Current attempts to measure the 21 cm power spectrum of neutral hydrogen during epoch reionization (EoR) are limited by systematics that produce measured upper limits above both thermal noise and expected cosmological signal. These arise from a combination observational, instrumental, analysis effects. In order further understand mitigate these effects, it is instructive explore different aspects existing data sets. One such aspect choice observing field. To date, MWA EoR...
Interferometric experiments designed to detect the highly redshifted 21-cm signal from neutral hydrogen are producing increasingly stringent constraints on power spectrum, but some k-modes remain systematics-dominated. Mutual coupling is a major systematic that must be overcome in order signal, and simulations reproduce effects seen data can guide strategies for mitigating mutual coupling. In this paper, we analyse 12 nights of Hydrogen Epoch Reionization Array compare against include...
The 21 cm transition from neutral Hydrogen promises to be the best observational probe of Epoch Reionisation (EoR). This has led construction low-frequency radio interferometric arrays, such as Reionization Array (HERA), aimed at systematically mapping this emission for first time. Precision calibration, however, is a requirement in observations. Due spatial compactness HERA, array prone effects mutual coupling, which inevitably lead non-smooth calibration errors that contaminate data. When...
ABSTRACT We quantify the effect of radio frequency interference (RFI) on measurements 21-cm power spectrum during Epoch Reionization (EoR). Specifically, we investigate how structure RFI source emission generates contamination in higher order wave modes, which is much more problematic than smooth-spectrum foreground sources. Using a relatively optimistic EoR model, find that even single dim can overwhelm signal $\sim 10\, {\rm mK}^2$ for modes $0.1 \ \lt k 2 \, h\, Mpc}^{-1}$. If total...
Abstract We apply two methods to estimate the 21-cm bispectrum from data taken within Epoch of Reionisation (EoR) project Murchison Widefield Array (MWA). Using acquired with Phase II compact array allows a direct be undertaken on multiple redundantly spaced triangles antenna tiles, as well an based gridded uv -plane. The and estimators are applied 21 h high-band (167–197 MHz; z = 6.2–7.5) 2016 2017 observing seasons. Analytic predictions for bias variance point-source foregrounds derived....
As current- and next-generation astronomical instruments come online, they will generate an unprecedented deluge of data. Analyzing these data in real time presents unique conceptual computational challenges, their long-term storage archiving is scientifically essential for generating reliable, reproducible results. We present here the real-time processing (RTP) system Hydrogen Epoch Reionization Array (HERA), a radio interferometer endeavoring to provide first detection highly redshifted 21...
ABSTRACT Accurate modelling of the primary beam is an important but difficult task in radio astronomy. For high dynamic range problems such as 21 cm intensity mapping, small errors sidelobes, and spectral structure beams can translate into significant systematic errors. Realistic exhibit complex spatial structure, presenting a major challenge for measurement calibration methods. In this paper series, we present Bayesian framework to infer per-element patterns from interferometric...
ABSTRACT An important application of next-generation wide-field radio interferometers is making high dynamic range maps emission. Traditional deconvolution methods like CLEAN can give poor recovery diffuse structure, prompting the development alternatives Direct Optimal Mapping and m-mode analysis. In this paper, we propose an alternative Bayesian method to infer coefficients a full-sky spherical harmonic basis for drift-scan telescope with potentially thousands baselines that precisely...
A successful detection of the cosmological 21-cm signal from intensity mapping experiments (for example, during Epoch Reioinization or Cosmic Dawn) is contingent on suppression subtle systematic effects in data. Some these effects, with mutual coupling a major concern interferometric data, manifest temporal variability distinct that signal. Fringe-rate filtering -- time-based Fourier technique powerful tool for mitigating effects; however, fringe-rate filters also attenuate Analyses employ...
ABSTRACT 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 filters in fringe-rate (FR) space, pair local sidereal time. Applications FR filtering include separating correlated with rotating sky versus those relative ground, down-weighting emission primary beam sidelobes, and suppressing noise. causes noise...
We explore how chromatic RFI flags affect 21-cm power spectrum measurements. particularly study that are coarser than the analysis resolution. find such produce excess in EoR window much same way as residual RFI. use Fast Holographic Deconvolution (FHD) simulations to explain this a result of disruptions interferometric sampling function array. also these conjunction with Error Propagated Power Spectrum InterLeaved Observed Noise ($\varepsilon$ppsilon) show without modifying current flagging...
We explore error distributions in Epoch of Reionization 21-cm power spectrum estimators using a combination mathematical analysis and numerical simulations. provide closed form solutions for the individual bins 3d-power spectra two currently use field, which we designate as ``straight-square" ``cross-multiply" estimators. then demonstrate when corresponding spherically binned should (and not) have Gaussian distributions, requires appealing to nonstandard statements central limit theorem....