Source-finding for the Australian Square Kilometre Array Pathfinder

Abstract

The Australian Square Kilometre Array Pathfinder (ASKAP) presents a number of challenges in the area of source finding and cataloguing. The data rates and image sizes are very large, and require automated processing in a high-performance computing environment. This requires development of new tools, that are able to operate in such an environment and can reliably handle large datasets. These tools must also be able to accommodate the different types of observations ASKAP will make: continuum imaging, spectral-line imaging, transient imaging. The ASKAP project has developed a source-finder known as Selavy, built upon the Duchamp source-finder (Whiting 2012). Selavy incorporates a number of new features, which we describe here. Since distributed processing of large images and cubes will be essential, we describe the algorithms used to distribute the data, find an appropriate threshold and search to that threshold and form the final source catalogue. We describe the algorithm used to define a varying threshold that responds to the local, rather than global, noise conditions, and provide examples of its use. And we discuss the approach used to apply two-dimensional fits to detected sources, enabling more accurate parameterisation. These new features are compared for timing performance, where we show that their impact on the pipeline processing will be small, providing room for enhanced algorithms. We also discuss the development process for ASKAP source finding software. By the time of ASKAP operations, the ASKAP science community, through the Survey Science Projects, will have contributed important elements of the source finding pipeline, and the mechanisms in which this will be done are presented.

11 pages, 3 figures. Accepted by Publications of the Astronomical Society of Australia. To appear in the special issue on Source Finding & Visualisation. Minor typos fixed

References in corpus (4)

• EMU: Evolutionary Map of the Universe
• Compact continuum source-finding for next generation radio surveys
• Deep ATLAS radio observations of the CDFS-SWIRE field
• Duchamp: a 3D source finder for spectral-line data

Cited by in corpus (47)

• Australian Square Kilometre Array Pathfinder: I. System Description
• The Rapid ASKAP Continuum Survey I: Design and First Results
• SoFiA: a flexible source finder for 3D spectral line data
• WALLABY -- An SKA Pathfinder HI Survey
• Source finding in the era of the SKA (precursors): Aegean 2.0
• SoFiA 2 -- An automated, parallel HI source finding pipeline for the WALLABY survey
• Detecting Weak Spectral Lines in Interferometric Data through Matched Filtering
• The Australian Square Kilometre Array Pathfinder: System Architecture and Specifications of the Boolardy Engineering Test Array
• Broadband Radio Polarimetry and Faraday Rotation of 563 Extragalactic Radio Sources
• The Rapid ASKAP Continuum Survey IV: continuum imaging at 1367.5 MHz and the first data release of RACS-mid
• A circular polarisation survey for radio stars with the Australian SKA Pathfinder
• Square Kilometre Array Science Data Challenge 1: analysis and results
• The ASKAP/EMU Source Finding Data Challenge
• The scaling relations and star formation laws of ministarburst complexes
• First constraints on the AGN X-ray luminosity function at $z\sim 6$ from an eROSITA-detected quasar
• The First Large Absorption Survey in HI (FLASH): I. Science Goals and Survey Design
• WALLABY Early Science -- IV. ASKAP HI imaging of the nearby galaxy IC 5201
• Automated detection of extended sources in radio maps: progress from the SCORPIO survey
• Discovery of Peculiar Radio Morphologies with ASKAP using Unsupervised Machine Learning
• GASKAP-HI Pilot Survey Science III: An unbiased view of cold gas in the Small Magellanic Cloud
• GASKAP Pilot Survey Science II: ASKAP Zoom Observations of Galactic 21-cm Absorption
• Deep 20-GHz survey of the Chandra Deep Field South and SDSS Stripe 82: source catalogue and spectral properties
• ASKAP observations of multiple rapid scintillators reveal a degrees-long plasma filament
• A pilot survey for transients and variables with the Australian Square Kilometre Array Pathfinder
• A search for radio afterglows from gamma-ray bursts with the Australian Square Kilometre Array Pathfinder
• YOLO-CIANNA: Galaxy detection with deep learning in radio data. I. A new YOLO-inspired source detection method applied to the SKAO SDC1
• A pilot ASKAP survey for radio transients towards the Galactic Centre
• Radio Sources Segmentation and Classification with Deep Learning
• Radio Variable and Transient Sources on Minute Timescales in the ASKAP Pilot Surveys
• FLASH Pilot Survey: Detections of associated 21 cm HI absorption in GAMA galaxies at 0.42 < z <1.00
• Searching for stellar flares from low mass stars using ASKAP and TESS
• Hydra II: Characterisation of Aegean, Caesar, ProFound, PyBDSF, and Selavy source finders
• Radio Transients and Variables in the Tenth Deeper, Wider, Faster Observing Run
• Hydra I: An extensible multi-source-finder comparison and cataloguing tool
• Discovery of Odd Radio Circles and Other Peculiars in the First Year of the EMU Survey using Object Detection
• A Framework for HI Spectral Source Finding Using Distributed-Memory Supercomputing
• A search for HI absorption in distant star-forming galaxies with ASKAP-FLASH -- I. Selection and analysis of the radio sample
• Unveiling the Cosmic Dance of Repeated Nuclear Transient ASASSN-14ko: Insights from Multiwavelength Observations
• EMU and the DRAGNs I: A Catalogue of DRAGNs
• Astroinformatics Challenges from Next-generation Radio Continuum Surveys
• Survey-scale discovery-based research processes: Evaluating a bespoke visualisation environment for astronomical survey data
• A FLASH on Blazars: Capturing the Radio Realm of 4FGL Blazars with SKAO Pathfinders
• Magnetic Fields in the Shapley Supercluster Core with POSSUM: Challenging Model Predictions
• The life of central radio galaxies in clusters: AGN-ICM studies of eRASS1 clusters in the ASKAP fields
• Cross-correlating the EMU Pilot Survey 1 with CMB lensing: Constraints on cosmology and galaxy bias with harmonic-space power spectra
• The Evolutionary Map of the Universe Pilot Survey
• WALLABY Pilot Survey: HI source-finding with a machine learning framework