A5007124033- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Antenna Design and Optimization
- Radio Wave Propagation Studies
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Particle Accelerators and Free-Electron Lasers
- GNSS positioning and interference
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- Soil Moisture and Remote Sensing
- History and Developments in Astronomy
- Astrophysical Phenomena and Observations
- Superconducting and THz Device Technology
- Electromagnetic Compatibility and Measurements
- Scientific Research and Discoveries
- Astronomy and Astrophysical Research
- Microwave Engineering and Waveguides
- Electromagnetic Scattering and Analysis
- Particle Detector Development and Performance
- Synthetic Aperture Radar (SAR) Applications and Techniques
- Space Science and Extraterrestrial Life
- Stellar, planetary, and galactic studies
- Advanced Frequency and Time Standards
International Centre for Radio Astronomy Research
2012-2021
Curtin University
2012-2021
Institute of Radio Astronomy
2021
Canadian Institute for Theoretical Astrophysics
2016
University of Toronto
2016
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...
Astronomical wide-field imaging of interferometric radio data is computationally expensive, especially for the large volumes created by modern non-coplanar many-element arrays. We present a new imager that uses w-stacking algorithm and can make use w-snapshot algorithm. The performance dependences casa's w-projection our are analysed analytical functions derived describe required computing cost both imagers. On from Murchison Widefield Array, we find method to be an order magnitude faster...
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;...
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....
The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in new era multi-messenger astronomy. In this paper, we present event GW170817 and its SSS17a/DLT17ck (IAU label AT2017gfo) 14 Australian telescopes partner observatories as part Australian-based Australian-led research programs. We report early- late-time multi-wavelength observations, including optical imaging spectroscopy,...
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...
We describe a new low-frequency wideband radio survey of the southern sky. Observations covering 72-231MHz and Declinations south +30° have been performed with Murchison Widefield Array "extended" Phase I configuration over 2018-2020 will be processed to form data products including continuum polarisation images mosaics, multi-frequency catalogues, transient search data, ionospheric measurements. From pilot field described in this work, we publish an initial release 1,447 deg2 4 h≤ RA≤ 13 h,...
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...
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...
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 We describe the motivation and design details of ‘Phase II’ upgrade Murchison Widefield Array radio telescope. The expansion doubles to 256 number antenna tiles deployed in array. new enhance capabilities several key science areas. Seventy-two are a regular configuration near existing array core. These surface brightness sensitivity will improve ability estimate slope Epoch Reionisation power spectrum by factor ∼3.5. remaining 56 on long baselines, doubling maximum baseline...
ABSTRACT We introduce the Fast Holographic Deconvolution method for analyzing interferometric radio data. Our new is an extension of A-projection/software-holography/forward modeling analysis techniques and shares their precision deconvolution wide-field polarimetry, while being significantly faster than current implementations that use full direction-dependent antenna gains. Using data from MWA 32 prototype, we demonstrate effectiveness our algorithm. may be particularly important upcoming...
We present a Stokes I, Q and U survey at 189 MHz with the Murchison Widefield Array 32 element prototype covering 2400 deg2. The has 15.6 arcmin angular resolution achieves noise level of 15 mJy beam−1. demonstrate novel interferometric data analysis that involves calibration drift scan data, integration through co-addition warped snapshot images, deconvolution point-spread function forward modeling. point source catalog down to flux limit 4 Jy. detect polarization from only one sources, PMN...
We present the 21 cm power spectrum analysis approach of Murchison Widefield Array Epoch Reionization project. In this paper, we compare outputs multiple pipelines for purpose validating statistical limits cosmological hydrogen at redshifts between 6 and 12. Multiple, independent, data calibration reduction are used to make on a fiducial night data. Comparing imaging stages highlights differences in calibration, foreground subtraction calculation. The spectra found using these different...
Abstract We present the results of an approximately 6 100 deg 2 104–196 MHz radio sky survey performed with Murchison Widefield Array during instrument commissioning between 2012 September and December: MWACS. The data were taken as meridian drift scans two different 32-antenna sub-arrays that available period. covers 20.5 h < RA 8.5 h, − 58° Dec −14°over three frequency bands centred on 119, 150 180 MHz, image resolutions 6–3 arcmin. catalogue has 3 arcmin angular resolution a typical...
Using the final 128 antenna locations of Murchison Widefield Array (MWA), we calculate its sensitivity to Epoch Reionization (EoR) power spectrum red- shifted 21 cm emission for a fiducial model and provide tools any model. Our calculation takes into account synthesis rotation, chro- matic asymmetrical baseline effects, excludes modes that will be contaminated by foreground subtraction. For model, MWA capable 14{\sigma} detection EoR signal with one full season observation on two fields (900...
We present a search for transient and variable radio sources at 154 MHz with the Murchison Widefield Array 32-tile prototype. 51 images were obtained that cover field of view 1430 deg2 centred on Hydra A. The observations over three days in 2010 March 2011 April May. mean cadence was 26 min there additional temporal information day year time-scales. explore variability sample 105 low-frequency within field. Four bright (S > 6 Jy) candidate identified displayed low levels short time-scale (26...
We present deep polarimetric observations at 154 MHz with the Murchison Widefield Array (MWA), covering 625 deg^2 centered on RA=0 h, Dec=-27 deg. The sensitivity available in our allows an in-band, frequency-dependent analysis of polarized structure for first time long wavelengths. Our suggests that structures are dominated by intrinsic emission but may also have a foreground Faraday screen component. At these wavelengths, compactness MWA baseline distribution provides excellent snapshot to...
In this paper we present observations, simulations, and analysis demonstrating the direct connection between location of foreground emission on sky its in cosmological power spectra from interferometric redshifted 21 cm experiments. We begin with a heuristic formalism for understanding mapping coordinates into cylindrically averaged measurements used by experiments, focus effects instrument beam response associated sidelobes. then demonstrate analyzing both simulated observed data Murchison...
Abstract Interferometric arrays seeking to measure the 21 cm signal from epoch of reionization (EOR) must contend with overwhelmingly bright emission foreground sources. Accurate recovery will require precise calibration array, and several new avenues for have been pursued in recent years, including methods using redundancy antenna configuration. The newly upgraded Phase II Murchison Widefield Array (MWA) is first interferometer that has large numbers redundant baselines while retaining good...
Type III solar radio bursts are the Sun's most intense and frequent nonthermal emissions. They involve two critical problems in astrophysics, plasma physics, space physics: how collective processes produce radiation magnetic reconnection occurs changes energy into kinetic energy. Here events identified definitively Solar Dynamics Observatory UV-EUV data, with strong upward downward pairs of jets, current sheets, cusp-like geometries on top time-varying loops, outflows along open field lines....
We present the first spectroscopic images of solar radio transients from prototype for Murchison Widefield Array (MWA), observed on 2010 March 27. Our observations span instantaneous frequency band 170.9-201.6 MHz. Though our observing period is characterized as a `low' to `medium' activity, one broadband emission feature and numerous short-lived, narrowband, non-thermal features are evident. data represent significant advance in low imaging, enabling us follow spatial, spectral, temporal...
Using the new wideband capabilities of Australia Telescope Compact Array (ATCA), we obtain spectra for PKS 1718-649, a well-known gigahertz-peaked spectrum radio source. The observations, between approximately 1 and 10 GHz over three epochs spanning 21 months, reveal variability both above spectral peak at ~3 below peak. combination low high frequency cannot be easily explained using single absorption mechanism, such as free-free or synchrotron self-absorption. We find that 1718-649 its are...
We present the results of a survey for low frequency radio emission from 17 known exoplanetary systems with Murchison Widefield Array. This sample includes 13 that have not previously been targeted observations. detected no at 154 MHz, and put 3 sigma upper limits in range 15.2-112.5 mJy on this emission. also searched circularly polarised made detections, obtaining 3.4-49.9 mJy. These are comparable best existing literature translate to luminosity between 1.2 x 10^14 W 1.4 10^17 if is...