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A general framework to test gravity using galaxy clusters VI: Realistic galaxy formation simulations to study clusters in modified gravity

Mitchell, Myles A. and Arnold, Christian and Li, Baojiu (2022) 'A general framework to test gravity using galaxy clusters VI: Realistic galaxy formation simulations to study clusters in modified gravity.', Monthly Notices of Royal Astronomical Society, 514 (3). pp. 3349-3365.


We present a retuning of the IllustrisTNG baryonic physics model which can be used to run large-box realistic cosmological simulations with a lower resolution. This new model employs a lowered gas density threshold for star formation and reduced energy releases by stellar and black hole feedback. These changes ensure that our simulations can produce sufficient star formation to closely match the observed stellar and gas properties of galaxies and galaxy clusters, despite having ∼160 times lower mass resolution than the simulations used to tune the fiducial IllustrisTNG model. Using the retuned model, we have simulated Hu–Sawicki f(R) gravity within a 301.75 h−1 Mpc box. This is, to date, the largest simulation that incorporates both screened modified gravity and full baryonic physics, offering a large sample (∼500) of galaxy clusters and ∼8000 galaxy groups. We have reanalysed the effects of the f(R) fifth force on the scaling relations between the cluster mass and four observable proxies: the mass-weighted gas temperature, the Compton Y-parameter of the thermal Sunyaev–Zel’dovich effect, the X-ray analogue of the Y-parameter, and the X-ray luminosity. We show that a set of mappings between the f(R) scaling relations and their Lambda cold dark matter counterpart, which have been tested in a previous work using a much smaller cosmological volume, are accurate to within a few per cent for the Y-parameters and ≲7 per cent for the gas temperature for cluster-sized haloes (⁠1014M⊙≲M500≲1015M⊙⁠). These mappings will be important for unbiased constraints of gravity using the data from ongoing and upcoming cluster surveys.

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Publisher statement:© 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. 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.
Date accepted:20 May 2022
Date deposited:14 July 2022
Date of first online publication:07 June 2022
Date first made open access:14 July 2022

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