Simulation tests of galaxy cluster constraints on chameleon gravity

Abstract

We use two new hydrodynamical simulations of $\\Lambda$CDM and $f(R)$ gravity\nto test the methodology used by Wilcox et al. 2015 (W15) in constraining the\neffects of a fifth force on the profiles of clusters of galaxies. We construct\nrealistic simulated stacked weak lensing and X-ray surface brightness cluster\nprofiles from these cosmological simulations, and then use these data projected\nalong various lines-of-sight to test the spherical symmetry of our stacking\nprocedure. We also test the applicability of the NFW profile to model weak\nlensing profiles of clusters in $f(R)$ gravity. Finally, we test the validity\nof the analytical model developed in W15 against the simulated profiles.\nOverall, we find our methodology is robust and broadly agrees with these\nsimulated data. We also apply our full Markov Chain Monte Carlo (MCMC) analysis\nfrom W15 to our simulated X-ray and lensing profiles, providing consistent\nconstraints on the modified gravity parameters as obtained from the real\ncluster data, e.g. for our $\\Lambda$CDM simulation we obtain $|f_{\\rm{R}0}| <\n8.3 \\times 10^{-5}$ (95% CL), which is in good agreement with the W15\nmeasurement of $|f_{\\rm{R}0}| < 6 \\times 10^{-5}$. Overall, these tests confirm\nthe power of our methodology which can now be applied to larger cluster samples\navailable with the next generation surveys.\n