Strongly coupled dark energy cosmologies: preserving ΛCDM success and easing low-scale problems – II. Cosmological simulations

Abstract

In this second paper we present the first Nbody cosmological simulations of strongly coupled Dark Energy models (SCDEW), a class of models that alleviates theoretical issues related to the nature of dark energy. SCDEW models assume a strong coupling between Dark Energy (DE) and an ancillary Cold Dark Matter (CDM) component together with the presence of an uncoupled Warm Dark Matter component. The strong coupling between CDM and DE allows us to preserve small scale fluctuations even if the warm particle is quite light ($\approx 100$ eV). Our large scale simulations show that, for $10^{11}<M/M_\odot<10^{14}$, SCDEW haloes exhibit a number density and distribution similar to a standard Lambda Cold Dark Matter (LCDM) model, even though they have lower concentration parameters. High resolution simulation of a galactic halo ($M\sim 10^{12} M_{\odot} $) shows $\sim 60\%$ less substructures than its LCDM counterpart, but the same cuspy density profile. On the scale of galactic satellites ($M\sim 10^{9} M_{\odot}$) SCDEW haloes dramatically differ from LCDM. Due to the high thermal velocities of the WDM component they are almost devoid of any substructures and present strongly cored dark matter density profiles. These density cores extend for several hundreds of parsecs, in very good agreement with Milky Way satellites observations. Strongly coupled models, thanks to their ability to match observations on both large and small scales might represent a valid alternative to a simple LCDM model.