Hydrodynamical simulations of galaxy clusters in dark energy cosmologies - II. c-M relation

We use hydrodynamical 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 (Lambda CDM) model, two quintessence models with inverse power-law potentials (RP and SUGRA) and two extended quintessence (EQ) models, one with positive and one with negative coupling with gravity (EQp and EQn, respectively). All the models are normalized in order to match cosmic microwave background data from Wilkinson Microwave Anisotropy Probe 3. We fit both the dark matter only and the total mass profiles with an NFW profile, and recover the concentration of each halo from the fit using different definition. We consider both the complete catalogue of clusters and groups and subsamples of objects at different level of relaxation. We find that the definition itself of the concentration can lead to differences up to 20 per cent in its value and that these differences are smaller when more relaxed objects are considered. The c-M relation of our reference Lambda CDM model is in good agreement with the results in the literature, and relaxed objects have a higher normalization and a shallower slope with respect to the complete sample. The inclusion of baryon physics is found to influence high-mass systems more than low-mass ones, due to a higher concentration of baryons in the inner regions of massive haloes. For the different dark energy models, we find that for Lambda CDM, RP and SUGRA the normalization of the c-M relation is linked to the growth factor, with models having a higher value of sigma D-8(+) having also a higher normalization. This simple scheme is no longer valid for EQp and EQn because in these models a time-dependent effective gravitational interaction, whose redshift evolution depends on the sign of the coupling, is present. 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 can be in principle investigated through the analysis of the relation.