Multi-component DHOST analysis in galaxy clusters

Abstract

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.

Probing Vainsthein-screening gravity with galaxy clusters using internal kinematics and strong and weak lensing

“…The tension found by our analysis confirms the results of Pizzuti et al (2017) and Laudato et al (2021) which seem to indicate a preference of modified gravity with respect to GR for this cluster. However, is important to point out that Abell S1063 is not dynamically relaxed at all.…”

“…On the other hand, the relativistic coupling is constrained to be −0.12 +0.66 −0.67 (2𝜎), which reduces by a factor ∼ 2 the previous results of Sakstein et al (2016), obtained by a joint lensing and X-ray analyses of the same model over a sample of 58 galaxy clusters. The bounds are also comparable to the more recent constraints of Laudato et al (2021), which uses lensing and X-ray data of 13 X-ray-selected and 3 lensing-selected clusters from the CLASH sample, including MACS 1206 and Abell S1063, to fit a generalization of the model discussed in this paper in terms of two parameters 𝛼 𝐻 , 𝛽 1 . It is interesting to notice that the constraints obtained by Laudato et al (2021) for MACS 1206 seems to indicate a slight tension with GR which is not found by our analysis.…”

“…The bounds are also comparable to the more recent constraints of Laudato et al (2021), which uses lensing and X-ray data of 13 X-ray-selected and 3 lensing-selected clusters from the CLASH sample, including MACS 1206 and Abell S1063, to fit a generalization of the model discussed in this paper in terms of two parameters 𝛼 𝐻 , 𝛽 1 . It is interesting to notice that the constraints obtained by Laudato et al (2021) for MACS 1206 seems to indicate a slight tension with GR which is not found by our analysis.…”

Gravitational transitions via the explicitly broken symmetron screening mechanism

“…Galaxy clusters are the largest gravitationally bound structures of the Cosmic Web. Thanks to the various surveys using dynamical, kinematic and weak lensing tracers, galaxy clusters can be used as a powerful cosmological probe of gravitational theories [112,[117][118][119] and screening mechanisms [120][121][122].…”