Multi-component DHOST analysis in galaxy clusters
  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. 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 only and as a description
of both dark matter and dark energy. 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 (CLASH) program using two
complementary probes, namely X-ray and strong-and-weak gravitational lensing
observations. In mass modelling, we adopt a multi-component 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 dark energy over General Relativity. This model also appears
to alleviate the discrepancy present in General Relativity between X-ray
hydrostatic and lensing mass estimates. For the second scenario where gravity
acts as both dark energy and dark matter due to the partial breaking of the
Vainshtein screening mechanism at cluster scales, the model is statistically
disfavoured compared to General Relativity.
