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02673 am a22002533u 4500 |
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|a Nurgaliev, D.
|e author
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|a MIT Kavli Institute for Astrophysics and Space Research
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|a McDonald, Michael A.
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|a Miller, Eric D.
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|a Benson, Bradford A.
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|a Stubbs, C. W.
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|a Vikhlinin, A.
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|a McDonald, Michael A.
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|a Miller, Eric D
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|a A ROBUST QUANTIFICATION OF GALAXY CLUSTER MORPHOLOGY USING ASYMMETRY AND CENTRAL CONCENTRATION
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|b IOP Publishing,
|c 2015-02-03T16:54:16Z.
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|z Get fulltext
|u http://hdl.handle.net/1721.1/93732
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|a We present a novel quantitative scheme of cluster classification based on the morphological properties that are manifested in X-ray images. We use a conventional radial surface brightness concentration parameter (c [subscript SB]) as defined previously by others and a new asymmetry parameter, which we define in this paper. Our asymmetry parameter, which we refer to as photon asymmetry (A [subscript phot]), was developed as a robust substructure statistic for cluster observations with only a few thousand counts. To demonstrate that photon asymmetry exhibits better stability than currently popular power ratios and centroid shifts, we artificially degrade the X-ray image quality by (1) adding extra background counts, (2) eliminating a fraction of the counts, (3) increasing the width of the smoothing kernel, and (4) simulating cluster observations at higher redshift. The asymmetry statistic presented here has a smaller statistical uncertainty than competing substructure parameters, allowing for low levels of substructure to be measured with confidence. A [subscript phot] is less sensitive to the total number of counts than competing substructure statistics, making it an ideal candidate for quantifying substructure in samples of distant clusters covering a wide range of observational signal-to-noise ratios. Additionally, we show that the asymmetry-concentration classification separates relaxed, cool-core clusters from morphologically disturbed mergers, in agreement with by-eye classifications. Our algorithms, freely available as Python scripts (https://github.com/ndaniyar/aphot), are completely automatic and can be used to rapidly classify galaxy cluster morphology for large numbers of clusters without human intervention.
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|a National Aeronautics and Space Administration (Hubble Fellowship Grant HST-HF51308.01-A)
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|a en_US
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|a Article
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|t The Astrophysical Journal
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