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DC Field | Value | Language |
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dc.contributor.author | Roberts, David H | - |
dc.contributor.author | Saripalli, Lakshmi | - |
dc.contributor.author | Subrahmanyan, Ravi | - |
dc.date.accessioned | 2017-07-26T11:25:05Z | - |
dc.date.available | 2017-07-26T11:25:05Z | - |
dc.date.issued | 2016-10-27 | - |
dc.identifier.citation | Proceedings of the IAU General Assembly, Astronomy in Focus meeting Volume 29B, held in 2015, Edited by Piero Benvenuti pp. 319-320, 2016 | en_US |
dc.identifier.issn | 1743-9213 | - |
dc.identifier.uri | http://hdl.handle.net/2289/6682 | - |
dc.description | Restricted Access. | en_US |
dc.description.abstract | Coalescence of supermassive black holes (SMBHs) in galaxy mergers is potentially the dominant contributor to the low frequency gravitational wave background (GWB). It was proposed by Merritt & Ekers that X-shaped radio galaxies are signposts of such coalescences and that their abundance might be used to predict the magnitude of the GWB. Cheung identified a sample of 100 candidate X-shaped radio galaxies using the NRAO FIRST survey; these are small-axial-ratio extended radio sources with off-axis emission. In Roberts et al. we made radio images of 52 of these sources with resolution of about 1 arcsecond using archival Very Large Array data. Fifty-one of the 52 were observed at 1.4 GHz, seven were observed at 1.4 and 5 GHz, and one was observed only at 5 GHz. Our higher resolution VLA images along with FIRST survey images of the sources in the sample reveal that extended extragalactic radio sources with small axial ratios are largely (60%) cases of double radio sources with twin lobes that have off-axis extensions, usually with inversion-symmetric structure. The available radio images indicate that at most 20% of sources might be genuine X-shaped radio sources that could have formed by a restarting of beams in a new direction following an interruption and axis flip. The remaining 20% are in neither of these categories. These images indicate that at most a small fraction of the candidates might be genuine X-shaped radio sources that were formed by a restarting of beams in a new direction following a major merger, or by spin drift caused by BH-BH interaction. This suggests that fewer than 1.3% of extended radio sources appear to be candidates for genuine axis reorientations (“spin flips”), or 2.2% if possible “axis drift” sources are included, much smaller than the 7% suggested by Leahy & Parma. Thus, the associated GWB may be substantially smaller than previous estimates. These results can be used to normalize detailed calculations of the SMBH coalescence rate and the GWB. | en_US |
dc.language.iso | en | en_US |
dc.publisher | Cambridge University Press for International Astronomical Union | en_US |
dc.relation.uri | http://adsabs.harvard.edu/abs/2016IAUFM..29B.319R | en_US |
dc.relation.uri | https://www.cambridge.org/core/journals/proceedings-of-the-international-astronomical-union/article/xshaped-radio-galaxies-and-the-nanohertz-gravitational-wave-background/E9FF32F04DFA5174A39712335434DDF2 | en_US |
dc.rights | 2016 International Astronomical Union | en_US |
dc.subject | supermassive back holes | en_US |
dc.title | X-Shaped Radio Galaxies and the Nanohertz gravitational wave background | en_US |
dc.type | Article | en_US |
Appears in Collections: | Research Papers (A&A) |
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File | Description | Size | Format | |
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2016_IAUGenass_29B_319.pdf Restricted Access | Restriced Access | 131.98 kB | Adobe PDF | View/Open Request a copy |
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