Interferometric Imaging with the 32 Element Murchison Wide-Field Array

Ord, S. M.; Mitchell, D. A.; Wayth, R. B.; Greenhill, L. J.; Bernardi, G.; Gleadow, Stewart J.; Edgar, Richard G.; Clark, Michael A.; Allen, G.; Arcus, W.; Benkevitch, L. V.; Bowman, Judd D.; Briggs, F.; Bunton, John D.; Burns, S.; Cappallo, R. J.; Coles, W. A.; Corey, B. E.; deSouza, L.; Doeleman, Sheperd S.; Derome, M.; Deshpande, A. A.; Emrich, D.; Goeke, R.; Gopalakrishna, M. R.; Herne, D.; Hewitt, Jacqueline N.; Kamini, P. A.; Kaplan, David L.; Kasper, J. C.; Kincaid, B. B.; Kocz, J.; Kowald, E.; Kratzenberg, E.; Kumar, Deepak; Lonsdale, Colin J.; Lynch, M. J.; McWhirter, S. R.; Srinivasan, Madhavi; Matejek, Michael; Morales, M. F.; Morgan, E.; Oberoi, D.; Pathikulangara, J.; Prabu, T.; Rogers, A. E. E.; Roshi, A.; Salah, J. E.; Schinkel, A.; Shankar, N. Udaya; Srivani, K. S.; Stevens, J.; Tingay, S. J.; Vaccarella, Annino; Waterson, M.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.

doi:10.1086/657160

Cited by 52 publications

(51 citation statements)

References 19 publications

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“…Such comparison provides insight into the strengths and weaknesses of the pipelines, as well as confirmation of results. The analysis discussed so far has been based on the FHD-to-òppsilon pipeline, and here we compare with the Real Time System (RTS, Mitchell et al 2008;Ord et al 2010) to Cosmological H I Power Spectrum (CHIPS, Trott et al 2016) pipeline.…”

Section: Comparison With Reference Pipelinementioning

confidence: 99%

First Season Mwa Eor Power Spectrum Results at Redshift 7

Beardsley

Hazelton

Sullivan

et al. 2016

ApJ

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The Murchison Widefield Array (MWA) has collected hundreds of hours of Epoch of Reionization (EoR) data and now faces the challenge of overcoming foreground and systematic contamination to reduce the data to a cosmological measurement. We introduce several novel analysis techniques, such as cable reflection calibration, hyper-resolution gridding kernels, diffuse foreground model subtraction, and quality control methods. Each change to the analysis pipeline is tested against a two-dimensional power spectrum figure of merit to demonstrate improvement. We incorporate the new techniques into a deep integration of 32 hoursof MWA data. This data set is used to place a systematic-limited upper limit on the cosmological power spectrum of  D2.7 10 2 4 mK 2 at k = 0.27 h Mpc −1 and z = 7.1, consistent with other published limits, and a modest improvement (factor of 1.4) over previous MWA results. From this deep analysis, we have identified a list of improvements to be made to our EoR data analysis strategies. These improvements will be implemented in the future and detailed in upcoming publications.

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Section: Comparison With Reference Pipelinementioning

confidence: 99%

First Season Mwa Eor Power Spectrum Results at Redshift 7

Beardsley

Hazelton

Sullivan

et al. 2016

ApJ

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185

207

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“…These can be divided broadly into two categories: image based and visibility based pipelines. For foreground subtraction and imaging these pipelines use the following imaging algorithms: Real Time System (Mitchell et al 2008;Ord et al 2010) and Fast Holographic Deconvolution .…”

Section: Analysis Of Mwa Datamentioning

confidence: 99%

DELAY SPECTRUM WITH PHASE-TRACKING ARRAYS: EXTRACTING THE H i POWER SPECTRUM FROM THE EPOCH OF REIONIZATION

Paul

Sethi

Morales

et al. 2016

ApJ

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The detection of redshifted 21 cm emission from the epoch of reionization (EoR) is a challenging task owing to strong foregrounds that dominate the signal. In this paper, we propose a general method, based on the delay spectrum approach, to extract H I power spectra that are applicable to tracking observations using an imaging radio interferometer ("Delay Spectrum with Imaging Arrays"). Our method is based on modeling the H I signal taking into account the impact of wide field effects such as the w-term, which are then used as appropriate weights in cross-correlating the measured visibilities. Our method is applicable to any radio interferometer that tracks a phase center and could be utilized for arrays such as the Murchison Widefield Array (MWA), Low Frequency Array (LOFAR), Giant Meterwave Radio Telescope (GMRT), Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER), and HERA. In the literature the delay spectrum approach has been implemented for near-redundant baselines using drift scan observations. In this paper we explore the scheme for non-redundant tracking arrays. This is the first application of delay spectrum methodology to such data to extract the H I signal. We analyze 3 hr of MWA tracking data on the EoR1 field. We present both two-dimensional ( k k , ) and onedimensional (k) power spectra from the analysis. Our results are in agreement with the findings of other pipelines developed to analyze the MWA EoR data.

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“…Strong residual instrumental polarization effects have indeed been seen in the MWA. A long‐standing issue here is that calibration gain values for an MWA pointing angle do not transfer to other pointing angles [ Ord et al , ]. Attempts to do so manifest most prominently as instrumental leakage in Stokes Q caused by “ X ” and “ Y ” beam patterns being very different from that predicted by simple pattern multiplication model.…”

Section: Introductionmentioning

confidence: 99%

Understanding instrumental Stokes leakage in Murchison Widefield Array polarimetry

et al. 2015

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This paper offers an electromagnetic, more specifically array theory, perspective on understanding strong instrumental polarization effects for planar low-frequency "aperture arrays" with the Murchison Widefield Array (MWA) as an example. A long-standing issue that has been seen here is significant instrumental Stokes leakage after calibration, particularly in Stokes Q at high frequencies. A simple model that accounts for interelement mutual coupling is presented which explains the prominence of Q leakage seen when the array is scanned away from zenith in the principal planes. On these planes, the model predicts current imbalance in the X (E-W) and Y (N-S) dipoles and hence the Q leakage. Although helpful in concept, we find that this model is inadequate to explain the full details of the observation data. This finding motivates further experimentation with more rigorous models that account for both mutual coupling and embedded element patterns. Two more rigorous models are discussed: the "full" and "average" embedded element patterns. The viability of the full model is demonstrated by simulating current MWA practice of using a Hertzian dipole model as a Jones matrix estimate. We find that these results replicate the observed Q leakage to approximately 2 to 5%. Finally, we offer more direct indication for the level of improvement expected from upgrading the Jones matrix estimate with more rigorous models. Using the average embedded pattern as an estimate for the full model, we find that Q leakage of a few percent is achievable.

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Interferometric Imaging with the 32 Element Murchison Wide-Field Array

Cited by 52 publications

References 19 publications

First Season Mwa Eor Power Spectrum Results at Redshift 7

First Season Mwa Eor Power Spectrum Results at Redshift 7

DELAY SPECTRUM WITH PHASE-TRACKING ARRAYS: EXTRACTING THE H i POWER SPECTRUM FROM THE EPOCH OF REIONIZATION

Understanding instrumental Stokes leakage in Murchison Widefield Array polarimetry

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