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Selecting and modelling remnant AGNs with limited spectral coverage


Quici, B and Turner, RJ and Seymour, N and Hurley-Walker, N and Shabala, SS and Ishwara-Chandra, CH, Selecting and modelling remnant AGNs with limited spectral coverage, Monthly Notices of the Royal Astronomical Society, 514, (3) pp. 3466-3484. ISSN 0035-8711 (2022) [Refereed Article]

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Copyright Statement

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society Published by Oxford University Press on behalf of the Royal Astronomical Society.Copyright (2022) The Authors.

DOI: doi:10.1093/mnras/stac1328


Quantifying the energetics and lifetimes of remnant radio-loud active galactic nuclei (AGNs) is much more challenging than for active sources due to the added complexity of accurately determining the time since the central black hole switched off. Independent spectral modelling of remnant lobes enables the derivation of the remnant ratio, Rrem (i.e. ‘off-time/source age’); however, the requirement of high-frequency (≳5 GHz) coverage makes the application of this technique over large-area radio surveys difficult. In this work, we propose a new method, which relies on the observed brightness of backflow of Fanaroff–Riley type II lobes, combined with the Radio AGN in Semi-Analytic Environments (RAiSE) code, to measure the duration of the remnant phase. Sensitive radio observations of the remnant radio galaxy J2253-34 are obtained to provide a robust comparison of this technique with the canonical spectral analysis and modelling methods. We find that the remnant lifetimes modelled by each method are consistent; spectral modelling yields Rrem = 0.23 ± 0.02, compared to Rrem = 0.26 ± 0.02 from our new method. We examine the viability of applying our proposed technique to low-frequency radio surveys using mock radio source populations, and examine whether the technique is sensitive to any intrinsic properties of radio AGNs. Our results show that the technique can be used to robustly classify active and remnant populations, with the most confident predictions for the remnant ratio, and thus off-time, in the longest lived radio sources (>50 Myr) and those at higher redshifts (z > 0.1).

Item Details

Item Type:Refereed Article
Keywords:galaxies, jets, radio continuum
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Cosmology and extragalactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Turner, RJ (Dr Ross Turner)
ID Code:150711
Year Published:2022
Web of Science® Times Cited:1
Deposited By:Physics
Deposited On:2022-06-24
Last Modified:2022-08-10

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