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The Completeness and Reliability of Threshold and False-discovery Rate Source Extraction Algorithms for Compact Continuum Sources

Published online by Cambridge University Press:  02 January 2013

M. T. Huynh ,
A. Hopkins ,
R. Norris ,
P. Hancock ,
T. Murphy ,
R. Jurek  and
M. Whiting
M. T. Huynh*
Affiliation:
International Centre for Radio Astronomy Research, M468, University of Western Australia, Crawley, WA 6009, Australia
A. Hopkins
Affiliation:
Australian Astronomical Observatory, P.O. Box 296, Epping NSW 1710, Australia ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
R. Norris
Affiliation:
CSIRO Astronomy & Space Sciences, Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia
P. Hancock
Affiliation:
Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
T. Murphy
Affiliation:
Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia School of Information Technologies, The University of Sydney, NSW 2006, Australia ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
R. Jurek
Affiliation:
CSIRO Astronomy & Space Sciences, Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia
M. Whiting
Affiliation:
CSIRO Astronomy & Space Sciences, Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia
*
GCorresponding author. Email: minh.huynh@uwa.edu.au
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Abstract

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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 analysisradio continuum: generaltechniques: image processing
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 29 , Special Issue 3: Source Finding and Visualisation , 2012 , pp. 229 - 243
Copyright
Copyright © Astronomical Society of Australia 2012

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