The galaxy cluster concentration-mass relation in dark energy cosmologies

TL;DR

This study uses numerical simulations to explore how different dark energy models influence the concentration-mass relation in galaxy clusters, revealing effects of scalar field interactions on cluster properties beyond background cosmology.

Contribution

It provides the first detailed analysis of the c-M relation in extended quintessence models with non-minimal scalar-tensor couplings, highlighting their unique impact on cluster structure.

Findings

LambdaCDM c-M relation aligns with literature

Relaxed clusters have higher normalization and shallower slope

Coupling in EQ models affects the c-M normalization via gravity-scalar interaction

Abstract

We use numerical simulations of different dark energy cosmologies to investigate the concentration-mass (c-M) relation in galaxy clusters. In particular, we consider a reference Lambda cold dark matter (LambdaCDM) model, two models with dynamical dark energy, viewed as a quintessence scalar field [using a Ratra and Peebles (RP) and a supergravity (SUGRA) potential form], and two extended quintessence models, one with positive and one with negative coupling (EQp and EQn respectively), where the quintessence scalar field interacts non-minimally with gravity (scalar-tensor theories). All the models are normalized in order to match CMB data from Wilkinson Microwave Anisotropy Probe 3 (WMAP3). [Abridged] We consider both the complete catalog of clusters and groups and a subsample of relaxed objects. The c-M relation of our reference LambdaCDM model is in good agreement with the results in literature, and relaxed objects have a higher normalization and a shallower slope with respect to the complete sample. For the different dark energy models, we find that for LambdaCDM, RP and SUGRA the normalization of the c-M relation is linked to the growth factor D+ and the power spectrum normalization sigma8, with models having a higher value of sigma8 D+ having also a higher normalization. This simple scheme is no longer valid for EQp and EQn because in these models it is present a time dependent effective gravitational interaction, whose redshift evolution depends on the sign of the coupling. This leads to a decrease (increase) of the expected normalization in the EQp (EQn) model. This result shows a direct manifestation of the coupling between gravity and the quintessence scalar field characterizing EQ models that cannot be seen at the background level but can be investigated in the non-linear regime.