Jacqueline N. Hewitt
A5076638185- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Antenna Design and Optimization
- Astronomy and Astrophysical Research
- Radio Wave Propagation Studies
- Pulsars and Gravitational Waves Research
- Superconducting and THz Device Technology
- Adaptive optics and wavefront sensing
- Gamma-ray bursts and supernovae
- Electromagnetic Compatibility and Measurements
- Geophysics and Gravity Measurements
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Particle Accelerators and Free-Electron Lasers
- Stellar, planetary, and galactic studies
- Millimeter-Wave Propagation and Modeling
- Solar and Space Plasma Dynamics
- Cosmology and Gravitation Theories
- History and Developments in Astronomy
- Antenna Design and Analysis
- Soil Moisture and Remote Sensing
- Astro and Planetary Science
- Gyrotron and Vacuum Electronics Research
- Particle accelerators and beam dynamics
Massachusetts Institute of Technology
2016-2025
University of Manchester
2024
Scuola Normale Superiore
2023
Kavli Institute for Particle Astrophysics and Cosmology
2009-2021
Moscow Institute of Thermal Technology
1999-2021
W.M. Keck Observatory
2013-2017
IIT@MIT
1997-2016
Vassar College
2006-2010
California Institute of Technology
2008
Northeast Radio Observatory Corporation
1988
The Murchison Widefield Array (MWA) is one of three Square Kilometre Precursor telescopes and located at the Radio-astronomy Observatory in Shire mid-west Western Australia, a location chosen for its extremely low levels radio frequency interference. MWA operates frequencies, 80-300 MHz, with processed bandwidth 30.72 MHz both linear polarisations, consists 128 aperture arrays (known as tiles) distributed over ~3 km diameter area. Novel hybrid hardware/software correlation real-time imaging...
The Hydrogen Epoch of Reionization Array (HERA) is a staged experiment to measure 21 cm emission from the primordial intergalactic medium (IGM) throughout cosmic reionization ($z=6-12$), and explore earlier epochs our Cosmic Dawn ($z\sim30$). During these epochs, early stars black holes heated ionized IGM, introducing fluctuations in emission. HERA designed characterize evolution power spectrum constrain timing morphology reionization, properties first galaxies, large-scale structure,...
The Murchison Widefield Array (MWA) is a dipole-based aperture array synthesis telescope designed to operate in the 80-300 MHz frequency range. It capable of wide range science investigations, but initially focused on three key projects. These are detection and characterization 3-dimensional brightness temperature fluctuations 21cm line neutral hydrogen during Epoch Reionization (EoR) at redshifts from 6 10, solar imaging remote sensing inner heliosphere via propagation effects signals...
Abstract Significant new opportunities for astrophysics and cosmology have been identified at low radio frequencies. The Murchison Widefield Array is the first telescope in southern hemisphere designed specifically to explore low-frequency astronomical sky between 80 300 MHz with arcminute angular resolution high survey efficiency. will enable advances along four key science themes, including searching redshifted 21-cm emission from EoR early Universe; Galactic extragalactic all-sky surveys;...
A number of experiments are currently working toward a measurement the 21 cm signal from epoch reionization (EoR). Whether or not these deliver detection cosmological emission, their limited sensitivity will prevent them providing detailed information about astrophysics reionization. In this work, we consider what types measurements be enabled by next generation larger EoR telescopes. To calculate type constraints that possible with such arrays, use simple models for instrument, foreground...
The Murchison Widefield Array (MWA) has collected hundreds of hours Epoch Reionization (EoR) data and now faces the challenge overcoming foreground systematic contamination to reduce a cosmological measurement. We introduce several novel analysis techniques such as cable reflection calibration, hyper-resolution gridding kernels, diffuse model subtraction, quality control methods. Each change pipeline is tested against two dimensional power spectrum figure merit demonstrate improvement....
Abstract We report upper limits on the Epoch of Reionization 21 cm power spectrum at redshifts 7.9 and 10.4 with 18 nights data (∼36 hr integration) from Phase I Hydrogen Array (HERA). The show evidence for systematics that can be largely suppressed systematic models down to a dynamic range ∼10 9 respect peak foreground power. This yields 95% confidence limit <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi...
Abstract Recently, the Hydrogen Epoch of Reionization Array (HERA) has produced experiment’s first upper limits on power spectrum 21 cm fluctuations at z ∼ 8 and 10. Here, we use several independent theoretical models to infer constraints intergalactic medium (IGM) galaxies during epoch reionization from these limits. We find that IGM must have been heated above adiabatic-cooling threshold by 8, uncertainties about ionization radio background. Combining HERA with complementary observations...
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...
Optical photometry is presented for the quadruple gravitational lens PG1115+080. A preliminary reduction of data taken from November 1995 to June 1996 gives component ``C'' leading ``B'' by 23.7+/-3.4 days and components ``A1'' ``A2'' 9.4 days. range models has been fit image positions, none which an adequate fit. The best fitting most physically plausible these, taking lensing galaxy associated group galaxies be singular isothermal spheres, a Hubble constant 42 km/s/Mpc Omega=1, with...
We present techniques for bridging the gap between idealized inverse covariance weighted quadratic estimation of 21 cm power spectra and real-world challenges presented universally by interferometric observation. By carefully evaluating various estimators adapting our large but incomplete data sets, we develop a robust spectrum framework that preserves so-called "Epoch Reionization (EoR) window" keeps track estimator errors covariances. apply method to observations from 32-tile prototype...
Subtraction of astrophysical foreground contamination from "dirty" sky maps produced by simulated measurements the Murchison Widefield Array (MWA) has been performed fitting a 3rd-order polynomial along spectral dimension each pixel in data cubes. The simulations are first to include unavoidable instrumental effects frequency-dependent primary antenna beams and synthesized array beams. They recover one-dimensional spherically-binned input redshifted 21 cm power spectrum within approximately...
In this paper we explore for the first time relative magnitudes of three fundamental sources uncertainty, namely, foreground contamination, thermal noise and sample variance in detecting HI power spectrum from Epoch Reionization (EoR). We derive limits on sensitivity a Fourier synthesis telescope to detect EoR based its array configuration statistical representation images made by instrument. use Murchison Widefield Array (MWA) our studies. Using unified framework estimating signal...
The Murchison Widefield Array (MWA) is a new low-frequency interferometric radio telescope built in Western Australia at one of the locations future Square Kilometre (SKA). We describe automated radio-frequency interference (RFI) detection strategy implemented for MWA, which based on AOFlagger platform, and present 72-231-MHz RFI statistics from 10 observing nights. removes 1.1% data. digital TV (DTV) observed 3% time due to occasional ionospheric or atmospheric propagation. After excision,...
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...
The separation of the faint cosmological background signal from bright astrophysical foregrounds remains one most daunting challenges mapping high-redshift intergalactic medium with redshifted 21 cm line neutral hydrogen. Advances in and modeling diffuse point source have improved subtraction accuracy, but no scheme is perfect. Precisely quantifying errors error correlations due to missubtracted allows for both rigorous analysis power spectrum maximal isolation "EoR window" foreground...
Detection of the cosmological neutral hydrogen signal from Epoch Reionization, and estimation its basic physical parameters, is principal scientific aim many current low-frequency radio telescopes. Here we describe Cosmological HI Power Spectrum Estimator (CHIPS), an algorithm developed implemented with data Murchison Widefield Array (MWA), to compute two-dimensional spherically-averaged power spectrum brightness temperature fluctuations. The motivations for CHIPS are application realistic...
Detection of 21~cm emission HI from the epoch reionization, at redshifts z>6, is limited primarily by foreground emission. We investigate signatures wide-field measurements and an all-sky model using delay spectrum technique that maps to object locations through signal delays between antenna pairs. demonstrate interferometric are inherently sensitive all scales, including largest angular owing nature measurements. These effects generic observations but shapes impact their amplitudes...
We present first results from radio observations with the Murchison Widefield Array seeking to constrain power spectrum of 21 cm brightness temperature fluctuations between redshifts 11.6 and 17.9 (113 75 MHz). 3 h were conducted over two nights significantly different levels ionospheric activity. use these data assess impact systematic errors at low frequency, including ionosphere radio-frequency interference, on a measurement. find that after 1–3 integration presented here, our...
We study the impact of sky-based calibration errors from source mismodelling on 21 cm power spectrum measurements with an interferometer and propose a method for suppressing their effects. While emission faint sources that are not accounted in catalogues is believed to be spectrally smooth, deviations true visibilities model not, due inherent chromaticity interferometer's sky response (the 'wedge'). Thus, unmodelled foregrounds, below confusion limit many instruments, introduce frequency...
Abstract This paper presents the design and deployment of Hydrogen Epoch Reionization Array (HERA) phase II system. HERA is designed as a staged experiment targeting 21 cm emission measurements Reionization. First results from I array are published early 2022, system nearing completion. We describe discuss progress on commissioning future upgrades. As designated Square Kilometre pathfinder instrument, we also show number “case studies” that investigate systematics seen while system, which...
This paper explores the potential for statistical epoch of reionization (EOR) measurements using wide-field radio observations. New developments in low-frequency instrumentation and signal processing allow very sensitive EOR measurements, analysis techniques enabled by these advances offer natural ways separating from residual foreground emission. introduces enabling technologies proposes an technique designed to make optimal use capabilities next-generation arrays. The observations we...
view Abstract Citations (152) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Time Delay of Gravitational Lens 0957+561. I. Methodology and Analysis Optical Photometric Data Press, William H. ; Rybicki, George B. Hewitt, Jacqueline N. When a data set's underlying covariance function (autocorrelation) can be estimated, one construct from the set global X^2^ statistic that takes into account expected statistical relationship between all...
Statistical observations of the epoch reionization (EOR) power spectrum provide a rich data set for understanding transition from cosmic "dark ages" to ionized universe we see today. EOR have become an active area experimental cosmology, and three first generation observatories--MWA, PAST, LOFAR--are currently under development. In this paper quantitative calculation dimensional sensitivity, incorporating design parameters planned array. This is then used explore constraints these can place...