Looking for Traces of Nonminimally Coupled Dark Matter in the X-COP Galaxy Clusters Sample

Abstract

We look for possible evidence of a nonminimal coupling (NMC) between dark matter (DM) and gravity using data from the X-COP compilation of galaxy clusters. We consider a theoretically motivated NMC that may dynamically arise from the collective behavior of the coarse-grained DM field (e.g., via Bose–Einstein condensation) with averaging/coherence length L _NMC . In the Newtonian limit, the NMC modifies the Poisson equation by a term ${L}_{\mathrm{NMC}}^{2}{{\rm{\nabla }}}^{2}\rho $ proportional to the Laplacian of the DM density itself. We show that this term, when acting as a perturbation over the standard Navarro–Frenk–White (NFW) profile of cold DM particles, can yield DM halo density profiles capable of correctly fitting galaxy clusters’ pressure profiles with an accuracy comparable to and, in some cases, even better than the standard cold DM NFW profile. We also show that the observed relation between the NMC length scale and the virial mass found in Gandolfi et al. for late-type galaxies is consistent with the relation we find in the current work, suggesting that the previously determined power-law scaling law holds up to galaxy cluster mass scales.

Keywords

• Cold dark matter
• Galaxy clusters
• Dark matter
• Non-standard theories of gravity
• Cosmology