Constraining chameleon screening using galaxy cluster dynamics

We constrain the chameleon screening mechanism in galaxy clusters, essentially obtaining limits on the coupling strength β and the asymptotic value of the field ϕ∞. For this purpose, we utilized a collection of the nine relaxed galaxy clusters within the X-COP compilation in the redshift range of z ≤ 0.1. We implement the formalism assuming a Navarro-Frenk-White mass profile for the dark matter density and study the degeneracy present between the mass M500 and the chameleon coupling with a high degree of improvement in the constraints for excluded parameter space. We recast our constrain to an upper limit on the scalaron field in fðRÞ subclass of models of jfR0j ≤ 9.2 × 10−6, using all the nine clusters and jfR0j ≤ 1.2 × 10−5 using only five clusters with Weak lensing priors taken into account, at a 95% confidence level. These bounds are consistent with existing limits in the literature and tighter than the constraints obtained with the same method by previous studies.