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

Abstract

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 $\Xi_1$ parameter in the small scale, which modifies the hydrostatic equilibrium. We utilize the well-compiled X-COP catalog consisting of 12 clusters with Intra Cluster Medium (ICM) pressure profile by Sunyaev-Zeldovich 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, $\sim 2\sigma$ significance for a deviation from the standard scenario in 4 of the clusters. However, in terms of Bayesian evidence, we find either equivalent or mild preference for GR. We estimate a joint constraint of $\Xi_1 = -0.030 \pm 0.043$ using 8 clusters, for a modification from a $\Lambda$CDM 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 $\Xi_1 = -0.061 \pm 0.074$. Finally, we comment on the tentative redshift dependence ($\Xi_1(z)$), finding a mild preference ($ \lesssim 2\sigma$) for the same.