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What defines a compact symmetric object? A carefully vetted sample of compact symmetric objects

Readhead, Anthony C. S. and Kiehlmann, Sebastian and Lister, Matthew L. and O'Neill, Sandra and Pearson, Timothy J. and Sheldahl, Evan and Siemiginowska, Aneta and Taylor, Gregory B. and Wilkinson, Peter N. (2021) What defines a compact symmetric object? A carefully vetted sample of compact symmetric objects. Astronomische Nachrichten, 342 (9-10). pp. 1185-1190. ISSN 0004-6337. doi:10.1002/asna.20210049.

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Compact symmetric objects (CSOs), young jetted-active galactic nuclei of overall projected size <1 kpc, are of great interest due to their youth and evolution. The classification was introduced to distinguish between ∼95% of powerful compact extragalactic radio sources in flux density limited samples that are dominated by asymmetric emission due to relativistic beaming from jets aligned close to the line of sight and ∼5% of objects that are not. The original classification criteria were (a) overall projected diameter smaller than 1 kpc, (b) identified center of activity, and (c) symmetric jet structure about the center. There is confusion and erosion of the value of the CSO classification due to misclassifications. Many jets contain compact bright features outside the core, resulting in a gigahertz peaked spectrum total spectrum and a “compact double” appearance, and some objects with jet axes aligned close to the line of sight appear symmetric because the approaching jet is projected on both sides of the core. To eliminate the confusion, we propose adding (d) slow radio variability and (e) low apparent velocity of bright features moving along the jets to the above CSO criteria. We are compiling a catalog of CSOs using these five criteria to eliminate the confusion of Doppler boosting.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Readhead, Anthony C. S.0000-0001-9152-961X
Kiehlmann, Sebastian0000-0001-6314-9177
Lister, Matthew L.0000-0003-1315-3412
Pearson, Timothy J.0000-0001-5213-6231
Siemiginowska, Aneta0000-0002-0905-7375
Taylor, Gregory B.0000-0001-6495-7731
Alternate Title:What defines a compact symmetric object? A carefully vetted sample of CSOs
Additional Information:© 2021 Wiley-VCH GmbH. Issue Online: 28 December 2021; Version of Record online: 08 November 2021; Manuscript accepted: 15 October 2021; Manuscript received: 15 October 2021. S.K. acknowledges support from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation programme under grant agreement No. 771282. S.O. gratefully acknowledges the support of the Caltech Summer Undergraduate Research Fellowship program. A.S. was supported by NASA contract NAS8-03060 to the Chandra X-ray Center.
Group:Astronomy Department
Funding AgencyGrant Number
European Research Council (ERC)771282
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Subject Keywords:active galaxies; compact symmetric objects; jetted-AGN
Issue or Number:9-10
Record Number:CaltechAUTHORS:20211201-150901197
Persistent URL:
Official Citation:What defines a compact symmetric object? A carefully vetted sample of compact symmetric objects. Readhead, A. C. S., Kiehlmann, S., Lister, M. L., et al. 2021, Astron. Nachr., 342, 1185.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112124
Deposited By: Tony Diaz
Deposited On:01 Dec 2021 17:52
Last Modified:04 Jan 2022 21:53

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