The Completeness and Reliability of Threshold and False-discovery Rate Source Extraction Algorithms for Compact Continuum Sources
M. T. Huynh A G , A. Hopkins B F , R. Norris C , P. Hancock D F , T. Murphy D E F , R. Jurek C and M. Whiting CA International Centre for Radio Astronomy Research, M468, University of Western Australia, Crawley, WA 6009, Australia
B Australian Astronomical Observatory, P.O. Box 296, Epping NSW 1710, Australia
C CSIRO Astronomy & Space Sciences, Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia
D Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia
E School of Information Technologies, The University of Sydney, NSW 2006, Australia
F ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
G Corresponding author. Email: minh.huynh@uwa.edu.au
Publications of the Astronomical Society of Australia 29(3) 229-243 https://doi.org/10.1071/AS11026
Submitted: 12 June 2011 Accepted: 19 October 2011 Published: 14 December 2011
Journal Compilation © Astronomical Society of Australia 2012
Abstract
The process of determining the number and characteristics of sources in astronomical images is so fundamental to a large range of astronomical problems that it is perhaps surprising that no standard procedure has ever been defined that has well-understood properties with a high degree of statistical rigour on completeness and reliability. The Evolutionary Map of the Universe (EMU) survey with the Australian Square Kilometre Array Pathfinder (ASKAP), a continuum survey of the Southern Hemisphere up to declination +30°, aims to utilise an automated source identification and measurement approach that is demonstrably optimal, to maximise the reliability, utility and robustness of the resulting radio source catalogues. A key stage in source extraction methods is the background estimation (background level and noise level) and the choice of a threshold high enough to reject false sources, yet not so high that the catalogues are significantly incomplete. In this analysis, we present results from testing the SExtractor, Selavy (Duchamp), and sfind source extraction tools on simulated data. In particular, the effects of background estimation, threshold and false-discovery rate settings are explored. For parameters that give similar completeness, we find the false-discovery rate method employed by sfind results in a more reliable catalogue compared to the peak threshold methods of SExtractor and Selavy.
Keywords: methods: data analysis — radio continuum: general — techniques: image processing
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