We present the first numerical-relativity simulations of binary neutron star (BNS) mergers admixed with dark matter (DM) based on constraint-solved initial data. Modeling DM as a non-interacting fermionic gas, we investigate the impact of varying DM fractions and particle masses on the merger dynamics, ejecta mass, post-merger remnant properties, and the emitted gravitational waves (GW). Our results indicate that the DM morphology (dense core or diluted halo) alters the merger outcome. DM-core scenarios tend toward prompt collapse, while DM-halo configurations develop a common envelope, modifying the environment in which the stars merge. GW signals from DM-halo configurations show deviations from analytical models when tidal deformability is calculated in a standard two-fluid framework, highlighting the need for refined models for systems with extended DM structures. These findings provide a basis for further exploration of DM role in BNS mergers and their associated GW emission.
Organized by: Catarina Cosme