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Particle content, radio-galaxy morphology and jet power: all radio-loud AGN are not equal

Croston, J.H.; Ineson, J. and Hardcastle, M.J. (2018). Particle content, radio-galaxy morphology and jet power: all radio-loud AGN are not equal. Monthly Notices of the Royal Astronomical Society, 476(2) pp. 1614–1623.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1093/mnras/sty274
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Abstract

Ongoing and future radio surveys aim to trace the evolution of black hole growth and feedback from active galactic nuclei (AGN) throughout cosmic time; however, there remain major uncertainties in translating radio luminosity functions into a reliable assessment of the energy input as a function of galaxy and/or dark matter halo mass. A crucial and long-standing problem is the composition of the radio-lobe plasma that traces AGN jet activity. In this paper, we carry out a systematic comparison of the plasma conditions in Fanaroff & Riley class I and II radio galaxies to demonstrate conclusively that their internal composition is systematically different. This difference is best explained by the presence of an energetically dominant proton population in the FRI, but not the FRII radio galaxies. We show that, as expected from this systematic difference in particle content, radio morphology also affects the jet-power/radio luminosity relationship, with FRII radio galaxies having a significantly lower ratio of jet power to radio luminosity than the FRI cluster radio sources used to derive jet-power scaling relations via X-ray cavity measurements. Finally we also demonstrate conclusively that lobe composition is unconnected to accretion mode (optical excitation class): the internal conditions of low- and high-excitation FRII radio lobes are indistinguishable. We conclude that inferences of populationwide AGN impact require careful assessment of the contribution of different jet sub classes, particularly given the increased diversity of jet evolutionary states expected to be present in deep, low-frequency radio surveys such as the LOFAR Two-Metre Sky Survey.

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; X-rays: galaxies: clusters
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: 53132
Depositing User: Judith Croston
Date Deposited: 07 Feb 2018 16:12
Last Modified: 13 Sep 2018 21:02
URI: http://oro.open.ac.uk/id/eprint/53132
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