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Remnant radio-loud AGN in the Herschel-ATLAS field

Mahatma, V. H.; Hardcastle, M. J.; Williams, W. L.; Brienza, M.; Brüggen, M.; Croston, J. H.; Gurkan, G.; Harwood, J. J.; Kunert-Bajraszewska, M.; Morganti, R.; Röttgering, H. J. A.; Shimwell, T. W. and Tasse, C. (2018). Remnant radio-loud AGN in the Herschel-ATLAS field. Monthly Notices of the Royal Astronomical Society, 475(4) pp. 4557–4578.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1093/mnras/sty025
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Abstract

Only a small fraction of observed active galactic nuclei (AGN) display large-scale radio emission associated with jets, yet these radio-loud AGN have become increasingly important in models of galaxy evolution. In determining the dynamics and energetics of the radio sources over cosmic time, a key question concerns what happens when their jets switch off. The resulting ‘remnant' radio-loud AGN have been surprisingly evasive in past radio surveys, and therefore statistical information on the population of radio-loud AGN in their dying phase is limited. In this paper, with the recent developments of Low-Frequency Array (LOFAR) and the Very Large Array, we are able to provide a systematically selected sample of remnant radio-loud AGN in the Herschel-ATLAS field. Using a simple core-detection method, we constrain the upper limit on the fraction of remnants in our radio-loud AGN sample to 9 per cent, implying that the extended lobe emission fades rapidly once the core/jets turn off. We also find that our remnant sample has a wide range of spectral indices (−1.5 ⩽ α1400150 ⩽ −0.5), confirming that the lobes of some remnants may possess flat spectra at low frequencies just as active sources do. We suggest that, even with the unprecedented sensitivity of LOFAR, our sample may still only contain the youngest of the remnant population.

Item Type: Journal Item
Copyright Holders: 2018 The Authors
ISSN: 1365-2966
Project Funding Details:
Funded Project NameProject IDFunding Body
Jet energy injection in galaxy groups and clusters - transfer of CG funding (Transfer in)ST/R00109X/1STFC (Science & Technology Facilities Council)
Keywords: galaxies: active; galaxies: jets; radio continuum: galaxies; methods: statistical
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Research Group: Astronomy
Item ID: 53133
Depositing User: Judith Croston
Date Deposited: 07 Feb 2018 16:20
Last Modified: 19 Jul 2019 06:17
URI: http://oro.open.ac.uk/id/eprint/53133
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