Influence of fermionic dark matter on the structural and tidal properties of neutron stars

Abstract We investigate the influence of ideal Fermi gas dark matter on the observable properties of neutron stars (NSs). Our analysis considers dark matter (DM) particle masses ( μ ) ranging from 0.2 GeV to 1 GeV and various DM mass fractions ( f ). By examining the coexistence of DM and baryonic matter (BM), we explore the formation of either a dense DM core or an extended dark halo within NSs. Our findings indicate that the resulting DM distribution depends critically on both μ and f . We systematically explore the parameter space of the fermionic DM model using two representative BM equations of state (EoSs) by applying constraints from NS radius measurements by the Neutron Star Interior Composition Explorer (NICER), observations of 2 M ⊙ NSs, and tidal deformability limits from the LIGO/Virgo collaboration. This comprehensive analysis enables us to exclude specific ranges of μ and f , demonstrating that the amount of accumulated DM must be relatively small to satisfy current astrophysical constraints.