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The Morphological Classification of Distant Radio Galaxies Explored with Three-Dimensional Simulations

Smith, Michael D., Donohoe, Justin (2019) The Morphological Classification of Distant Radio Galaxies Explored with Three-Dimensional Simulations. Monthly Notices of the Royal Astronomical Society, 490 (1). pp. 1363-1382. ISSN 0035-8711. (doi:10.1093/mnras/stz2525) (KAR id:76355)

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We explore the observational implications of a large systematic study of high-resolution three dimensional simulations of radio galaxies driven by supersonic jets. For this fiducial study, we employ non-relativistic hydrodynamic adiabatic flows from nozzles into a constant pressure-matched environment. Synchrotron emissivity is approximated via the thermal pressure of injected material. We find that the morphological classification of a simulated radio galaxy depends significantly on several factors with increasing distance (i.e. decreasing observed resolution) and decreasing orientation often causing re-classification from FR II (limb-brightened) to FR I (limb-darkened) type. We introduce the Lobe or Limb Brightening Index (LBI) to measure the radio lobe type more precisely. The jet density also has an influence as expected with lower density leading to broader and bridged lobe morphologies as well as brighter radio jets. Hence, relating observed source type to the intrinsic jet dynamics is not straightforward. Precession of the jet direction may also be responsible for wide relaxed sources with lower LBI and FR class as well as for X-shaped and double-double structures. Helical structures are not generated because the precession is usually too slow. We conclude that distant radio galaxies could appear systematically more limb-darkened due to merger-related re-direction and precession as well as due to the resolution limitation.

Item Type: Article
DOI/Identification number: 10.1093/mnras/stz2525
Uncontrolled keywords: hydrodynamics, galaxies: active, galaxies: jets, radio continuum: galaxies
Divisions: Divisions > Division of Natural Sciences > Physics and Astronomy
Depositing User: Michael Smith
Date Deposited: 11 Sep 2019 13:06 UTC
Last Modified: 03 Sep 2021 14:00 UTC
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Smith, Michael D.:
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