2022MNRAS.511.1878L

Extended theories of gravity with additional scalar degrees of freedom have recently acquired increasing interest due to the presence of a screening mechanism that allows suppressing at small scales (e.g. the Solar system scale) every modification restoring general relativity (GR). In this work, we consider a second-order extended theory of gravity belonging to the family of degenerate high-order scalar-tensor theories (DHOST) characterized by a partial breaking of the Vainshtein screening mechanism. We study this model in two different scenarios as a description of dark energy (DE) only and as a description of both dark matter (DM) and DE. Such scenarios have been tested here by analysing a sample of 16 high-mass galaxy clusters targeted by the cluster lensing and supernova survey with Hubble program using two complementary probes, namely X-ray and strong- and weak-gravitational lensing observations. In mass modelling, we adopt a multicomponent approach including hot gas and galactic stellar contributions. For the majority of the clusters in our sample, results show mild Bayesian evidence in favour of the DHOST model as a description of DE over GR. This model also appears to alleviate the discrepancy present in GR between X-ray hydrostatic and lensing mass estimates. For the second scenario, where gravity acts as both DE and DM due to the partial breaking of the Vainshtein screening mechanism at cluster scales, the model is statistically disfavoured compared to GR.