Scalable precision wide-field imaging in radio interferometry: I. uSARA validated on ASKAP data

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Abstract

In this work, we consider the unconstrained Sparsity Averaging Reweighted Analysis (uSARA) approach for wide-field radio-interferometric imaging via a parallelised and automated pipeline framework. We reconstruct images from real radio-interferometric observations obtained with the Australian Square Kilometre Array Pathfinder (ASKAP) and present these results in comparison to the widely-used WSClean. Our selected fields come from the ASKAP-EMU Pilot and Early Science surveys and contain several targets of primary interest: the merging galaxy cluster system Abell 3391-95, the merging galaxy cluster SPT-CL 2023-5535, and many extended, or bent-tail, radio galaxies, including PKS 2014-558, PKS 0625–545, and ESO 161-IG 007. All of these target sources exhibit complex radio emission with both compact and diffuse morphologies, making them ideal test subjects for SARA-based algorithmic reconstruction. The modern framework behind uSARA utilises parallelisation and automation to solve for the $w$-effect and efficiently compute the measurement operator, allowing for wide-field reconstruction over the full field-of-view of individual ASKAP beams (up to $\sim 3.3 ^{\circ}$ each). The precision capability of uSARA produces images with both super-resolution and enhanced sensitivity to diffuse components, surpassing traditional CLEAN algorithms which typically require a compromise between such yields. Our resulting monochromatic uSARA-ASKAP images of the selected data highlight both extended, diffuse emission and compact, filamentary emission at very high resolution (up to 2.2 arcsec), revealing never-before-seen structure in these target sources. Here we present a qualitative and quantitative validation of our uSARA-ASKAP images by comparing the structure of reconstructed sources and measurements of diffuse flux with results obtained from multi-scale WSClean.
Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Publication statusIn preparation - 2022

Keywords

  • techniques: image processing

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