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The environments of the radio galaxy population in simba

Thomas, Nicole; Davé, Romeel

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Romeel Davé


We investigate the environmental properties of the z = 0 radio galaxy population using the SIMBA cosmological hydrodynamic simulation. We identify centrals and satellites from a population of high and low excitation radio galaxies (HERGs and LERGs) in SIMBA, and study their global properties. We find that ∼20 per cent of radio galaxies are satellites, and that there are insignificant differences in the global properties of LERGs based on their central/satellite classification. HERG satellites display lower values of star formation, 1.4 GHz radio luminosity, and Eddington fractions than HERG centrals. We further investigate the environments of radio galaxies and show that HERGs typically live in less dense environments, similar to star-forming galaxies. The environments of high-mass LERGs are similar to non-radio galaxies, but low-mass LERGs live in underdense environments similar to HERGs. LERGs with overmassive black holes reside in the most dense environments, while HERGs with overmassive black holes reside in underdense environments. The richness of a LERG’s environment decreases with increasing Eddington fraction, and the environments of all radio galaxies do not depend on radio luminosity for P1.4 GHz<1024 W Hz−1⁠. Complementing these results, we find that LERGs cluster on the same scale as the total galaxy population, while multiple HERGs are not found within the same dark matter halo. Finally, we show that high density environments support the growth of HERGs rather than LERGs at z = 2. SIMBA predicts that with more sensitive surveys, we will find populations of radio galaxies in environments much similar to the total galaxy population.


Thomas, N., & Davé, R. (2022). The environments of the radio galaxy population in simba. Monthly Notices of the Royal Astronomical Society, 515(4), 5539 - 5555.

Journal Article Type Article
Acceptance Date Jul 27, 2022
Online Publication Date Aug 6, 2022
Publication Date 2022-10
Deposit Date Sep 28, 2022
Publicly Available Date Sep 29, 2022
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 515
Issue 4
Pages 5539 - 5555


Published Journal Article (Advance online version) (1.8 Mb)

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Copyright Statement
Advance online version This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

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