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

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 similar to 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 (similar to 500) of galaxy clusters and similar to 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 less than or similar to 7 per cent for the gas temperature for cluster-sized haloes (10(14) M-circle dot less than or similar to M-500 less than or similar to 10(15) M-circle dot). These mappings will be important for unbiased constraints of gravity using the data from ongoing and upcoming cluster surveys.

Automated summary

The study introduces a retuned IllustrisTNG baryonic physics model for large-box cosmological simulations with lower resolution, ensuring sufficient star formation to match observed galaxy properties. Using the retuned model, the largest simulation to date incorporating modified gravity and full baryonic physics was conducted, offering a substantial sample of galaxy clusters and groups. The effects of the modified gravity on the mass scaling relations in galaxy clusters were reanalyzed, providing accurate mappings for unbiased gravity constraints in future cluster surveys.