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How frequent are close supermassive binary black holes in powerful jet sources?

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Krause, MGH, Shabala, SS ORCID: 0000-0001-5064-0493, Hardcastle, MJ, Bicknell, GV, Bohringer, H, Chon, G, Nawaz, MA, Sarzi, M and Wagner, AY 2018 , 'How frequent are close supermassive binary black holes in powerful jet sources?' , Monthly Notices of the Royal Astronomical Society, vol. 482, no. 1 , pp. 240-261 , doi: 10.1093/mnras/sty2558.

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Abstract

Supermassive black hole binaries may be detectable by an upcoming suite of gravitational wave experiments. Their binary nature can also be revealed by radio jets via a short-period precession driven by the orbital motion as well as the geodetic precession at typically longer periods. We have investigated Karl G. Jansky Very Large Array and Multi-Element Radio Linked Interferometer Network (MERLIN) radio maps of powerful jet sources for morphological evidence of geodetic precession. For perhaps the best-studied source, Cygnus A, we find strong evidence for geodetic precession. Projection effects can enhance precession features, for which we find indications in strongly projected sources. For a complete sample of 33 3CR radio sources, we find strong evidence for jet precession in 24 cases (73 per cent). The morphology of the radio maps suggests that the precession periods are of the order of 106-107 yr. We consider different explanations for the morphological features and conclude that geodetic precession is the best explanation. The frequently observed gradual jet angle changes in samples of powerful blazars can be explained by orbital motion. Both observations can be explained simultaneously by postulating that a high fraction of powerful radio sources have subparsec supermassive black hole binaries. We consider complementary evidence and discuss if any jetted supermassive black hole with some indication of precession could be detected as individual gravitational wave source in the near future. This appears unlikely, with the possible exception of M87.

Item Type: Article
Authors/Creators:Krause, MGH and Shabala, SS and Hardcastle, MJ and Bicknell, GV and Bohringer, H and Chon, G and Nawaz, MA and Sarzi, M and Wagner, AY
Keywords: black hole physics, gravitational waves, galaxies: jets, radio continuum: galaxies
Journal or Publication Title: Monthly Notices of the Royal Astronomical Society
Publisher: Blackwell Publishing Ltd
ISSN: 0035-8711
DOI / ID Number: 10.1093/mnras/sty2558
Copyright Information:

Copyright 2018 The Authors. This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©:2018. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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