wsclean: an implementation of a fast, generic wide-field imager for radio astronomy

Offringa, A. R.; McKinley, B.; Hurley‐Walker, N.; Briggs, F.; Wayth, R. B.; Kaplan, David L.; Bell, M. E.; Lü, Feng; Neben, Abraham R.; Hughes, J. D.; Rhee, J.; Murphy, Tara; Bhat, N. D. R.; Bernardi, G.; Bowman, Judd D.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Emrich, D.; Ewall‐Wice, Aaron; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Hindson, L.; Johnston‐Hollitt, M.; Jacobs, Daniel; Kasper, J. C.; Kratzenberg, E.; Lenc, E.; Lonsdale, Colin J.; Lynch, M. J.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Kudryavtseva, N. A.; Oberoi, D.; Ord, S. M.; Pindor, B.; Procopio, P.; Prabu, T.; Riding, J.; Roshi, D. Anish; Shankar, N. Udaya; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Waterson, M.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.

doi:10.1093/mnras/stu1368

Cited by 739 publications

(479 citation statements)

References 29 publications

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“…No self‐calibration was performed on this data set. The full‐bandwidth data (30.72MHz) were then imaged and deconvolved using the WSCLEAN algorithm [ Offringa et al , ] to yield images of size 3072 × 3072 pixels, the pixel size being 0.75

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. The data were CLEANed up to a maximum of 20,000 iterations.…”

Section: Methodsmentioning

confidence: 99%

Power spectrum analysis of ionospheric fluctuations with the Murchison Widefield Array

et al. 2015

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Low-frequency, wide field-of-view (FOV) radio telescopes such as the Murchison Widefield Array (MWA) enable the ionosphere to be sampled at high spatial completeness. We present the results of the first power spectrum analysis of ionospheric fluctuations in MWA data, where we examined the position offsets of radio sources appearing in two data sets. The refractive shifts in the positions of celestial sources are proportional to spatial gradients in the electron column density transverse to the line of sight. These can be used to probe plasma structures and waves in the ionosphere. The regional (10-100 km) scales probed by the MWA, determined by the size of its FOV and the spatial density of radio sources (typically thousands in a single FOV), complement the global (100-1000 km) scales of GPS studies and local (0.01-1 km) scales of radar scattering measurements. Our data exhibit a range of complex structures and waves. Some fluctuations have the characteristics of traveling ionospheric disturbances, while others take the form of narrow, slowly drifting bands aligned along the Earth's magnetic field.

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^{'}

. The data were CLEANed up to a maximum of 20,000 iterations.…”

Section: Methodsmentioning

confidence: 99%

Power spectrum analysis of ionospheric fluctuations with the Murchison Widefield Array

et al. 2015

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“…Two rounds of self-calibration were then performed on the target scan, the first using a model from the TIFR GMRT Sky Survey (TGSS) Alternative Data Release (TGSS ADR, 9 Intema et al 2017). Multiscale imaging with Briggs 1.0 weighting was then performed using the WSClean tool (Offringa et al 2014). The subband with a central frequency of 150 MHz was flux calibrated using the integrated flux density measurements of point sources from the TGSS ADR.…”

Section: Radio Observationsmentioning

confidence: 99%

Investigating Galactic Supernova Remnant Candidates Using LOFAR

Driessen

Domček

Vink

et al. 2018

ApJ

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We investigate six supernova remnant (SNR) candidates-G51. 21+0.11, G52.37-0.70, G53.07+0.49, G53.41 +0.03, G53.84-0.75, and the possible shell around G54.1+0.3-in the Galactic plane using newly acquired LowFrequency Array High-band Antenna observations, as well as archival Westerbork Synthesis Radio Telescope and Very Large Array Galactic Plane Survey mosaics. We find that G52.37-0.70, G53.84-0.75, and the possible shell around pulsar wind nebula G54.1+0.3 are unlikely to be SNRs, while G53.07+0.49 remains a candidate SNR. G51.21+0.11 has a spectral index of α = − 0.7±0.21, but lacks X-ray observations and as such requires further investigation to confirm its nature. We confirm one candidate, G53.41+0.03, as a new SNR because it has a shelllike morphology, a radio spectral index of α = − 0.6±0.2 and it has the X-ray spectral characteristics of a 1000-8000year old SNR. The X-ray analysis was performed using archival XMM-Newton observations, which show that G53.41+0.03 has strong emission lines and is best characterized by a nonequilibrium ionization model, consistent with an SNR interpretation. Deep Arecibo radio telescope searches for a pulsar associated with G53.41 +0.03 resulted in no detection, but placed stringent upper limits on the flux density of such a source if it was beamed toward Earth.

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“…Much of the raw data processing for this work made use of custom software developed for use with the MWA. These include the algorithm AOFLAGGER for removing radio frequency interference [ Offringa et al , ] and the imaging algorithm WSCLEAN [ Offringa et al , ]. Details of the reduction process for data taken on the 26th and 28th can be found in Loi et al [] and A. Rowlinson et al (Limits on FRBs and other transient sources at 182 MHz using the Murchison Widefield Array, submitted to Monthly Notices of the Royal Astronomical Society , 2015), respectively, which describe the procedure for generating the final total intensity images that we analyze in the current work.…”

Section: Methodsmentioning

confidence: 99%

Density duct formation in the wake of a travelling ionospheric disturbance: Murchison Widefield Array observations

et al. 2016

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Geomagnetically aligned density structures with a range of sizes exist in the near‐Earth plasma environment, including 10–100 km wide VLF/HF wave‐ducting structures. Their small diameters and modest density enhancements make them difficult to observe, and there is limited evidence for any of the several formation mechanisms proposed to date. We present a case study of an event on 26 August 2014 where a travelling ionospheric disturbance (TID) shortly precedes the formation of a complex collection of field‐aligned ducts, using data obtained by the Murchison Widefield Array (MWA) radio telescope. Their spatiotemporal proximity leads us to suggest a causal interpretation. Geomagnetic conditions were quiet at the time, and no obvious triggers were noted. Growth of the structures proceeds rapidly, within 0.5 h of the passage of the TID, attaining their peak prominence 1–2 h later and persisting for several more hours until observations ended at local dawn. Analyses of the next 2 days show field‐aligned structures to be preferentially detectable under quiet rather than active geomagnetic conditions. We used a raster scanning strategy facilitated by the speed of electronic beamforming to expand the quasi‐instantaneous field of view of the MWA by a factor of 3. These observations represent the broadest angular coverage of the ionosphere by a radio telescope to date.

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wsclean: an implementation of a fast, generic wide-field imager for radio astronomy

Cited by 739 publications

References 29 publications

Power spectrum analysis of ionospheric fluctuations with the Murchison Widefield Array

Power spectrum analysis of ionospheric fluctuations with the Murchison Widefield Array

Investigating Galactic Supernova Remnant Candidates Using LOFAR

Density duct formation in the wake of a travelling ionospheric disturbance: Murchison Widefield Array observations

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