The effects on structure of a momentum coupling between dark matter and quintessence

Abstract: Given the mysterious nature of dark matter and dark energy, and the persistent tensions in cosmological data, it is worthwhile exploring more exotic physics in the dark sector, such as a momentum coupling between dark matter and dark energy, specifically in the form of a quintessence field. In this study, using collisionless N-body numerical simulations with a modified version of the RAMSES code, we follow up previous work to investigate the consequences of this model on dark matter halos and their substructures. We consider both the sign of the coupling and the imprints on structure formation and halo properties at a statistical level. We find that there is a clear enhancement (reduction) of substructure if the sign of the coupling is negative (positive) and that the dynamical state of the dark matter halos, particularly host halos, is undervirialised (overvirialised) at redshift zero when compared to uncoupled models or a reference $\Lambda$CDM simulation. Furthermore, positive coupling leads to less concentrated, less cuspy halos, whereas negative coupling leads to the opposite.