Testing generalized scalar-tensor theories of gravity with clusters of galaxies

We test the generalized scalar tensor theory in static systems, namely galaxy clusters. The degenerate higher-order scalar-tensor (DHOST) theory modifies the Newtonian potential through effective Newtonian constant and Ξ1 parameter in the small scale, which modifies the hydrostatic equilibrium. We utilize the well-compiled X-COP catalog consisting of 12 clusters with intracluster medium (ICM) pressure profile by Sunyaev-Zel'dovich effect data and temperature profile by x-ray data for each cluster. We perform a fully Bayesian analysis modeling Navarro-Frenk-White (NFW) for the mass profile, and the simplified Vikhlinin model for the electron density. Carefully selecting suitable clusters to present our results, we find a mild to moderate, i.e., ∼2σ significance for a deviation from the standard scenario in four of the clusters. However, in terms of Bayesian evidence, we find either equivalent or mild preference for GR. We estimate a joint constraint of Ξ1=-0.030±0.043 using eight clusters, for a modification from a ΛCDM scenario. This limit is in very good agreement with theoretical ones and an order of magnitude more stringent than the previous constraint obtained using clusters. We also quote a more conservative limit of Ξ1=-0.061±0.074. Finally, we comment on the tentative redshift dependence of the Ξ1 parameter.