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Investigating the spectral age problem with powerful radio galaxies

Mahatma, Vijay H; Hardcastle, Martin J; Croston, Judith H; Harwood, Jeremy; Ineson, Judith and Moldon, Javier (2020). Investigating the spectral age problem with powerful radio galaxies. Monthly Notices of the Royal Astronomical Society, 491(4) pp. 5015–5034.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1093/mnras/stz3396
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Abstract

The ‘spectral age problem’ is our systematic inability to reconcile the maximum cooling time of radiating electrons in the lobes of a radio galaxy with its age as modelled by the dynamical evolution of the lobes. While there are known uncertainties in the models that produce both age estimates, ‘spectral’ ages are commonly underestimated relative to dynamical ages, consequently leading to unreliable estimates of the time-averaged kinetic feedback of a powerful radio galaxy. In this work, we attempt to solve the spectral age problem by observing two cluster-centre powerful radio galaxies; 3C 320 and 3C 444. With high-resolution broad-band Karl G. Jansky Very Large Array observations of the radio sources and deep XMM–Newton and Chandra observations of their hot intracluster media, coupled with the use of an analytic model, we robustly determine their spectral and dynamical ages. After finding self-consistent dynamical models that agree with our observational constraints, and accounting for sub-equipartition magnetic fields, we find that our spectral ages are still underestimated by a factor of two at least. Equipartition magnetic fields will underestimate the spectral age by factors of up to ∼20. The turbulent mixing of electron populations in the radio lobes is likely to be the main remaining factor in the spectral age/dynamical age discrepancy, and must be accounted for in the study of large samples of powerful radio galaxies.

Item Type: Journal Item
Copyright Holders: 2019 The Authors
ISSN: 1365-2966
Extra Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2019 The Authors.Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Keywords: radiation mechanisms: non-thermal; shock waves; observational methods; active galaxies; galaxy clusters; intracluster medium; galactic jets
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
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Item ID: 68664
SWORD Depositor: Jisc Publications-Router
Depositing User: Judith Croston
Date Deposited: 06 Jan 2020 11:55
Last Modified: 24 Jun 2020 14:01
URI: http://oro.open.ac.uk/id/eprint/68664
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