Structure of dark matter halos in warm dark matter models and in models with long-lived charged massive particles

Abstract

We study the formation of non-linear structures in Warm Dark Matter (WDM)\nmodels and in a Long-Lived Charged Massive Particle (CHAMP) model. CHAMPs with\na decay lifetime of about 1 yr induce characteristic suppression in the matter\npower spectrum at subgalactic scales through acoustic oscillations in the\nthermal background. We explore structure formation in such a model. We also\nstudy three WDM models, where the dark matter particles are produced through\nthe following mechanisms: i) WDM particles are produced in the thermal\nbackground and then kinematically decoupled; ii) WDM particles are fermions\nproduced by the decay of thermal heavy bosons; and iii) WDM particles are\nproduced by the decay of non-relativistic heavy particles. We show that the\nlinear matter power spectra for the three models are all characterised by the\ncomoving Jeans scale at the matter-radiation equality. Furthermore, we can also\ndescribe the linear matter power spectrum for the Long-Lived CHAMP model in\nterms of a suitably defined characteristic cut-off scale k_{Ch}, similarly to\nthe WDM models. We perform large cosmological N-body simulations to study the\nnon-linear growth of structures in these four models. We compare the halo mass\nfunctions, the subhalo mass functions, and the radial distributions of subhalos\nin simulated Milky Way-size halos. We study the models with k_{cut}=51, 410,\n820 h/Mpc, and confirm that these statistics are indeed similar between the\ndifferent WDM models and the Long-Lived CHAMP model. The result suggests that\nthe cut-off scale k_{cut} not only characterises the linear power spectra but\nalso can be used to predict the non-linear clustering properties. The radial\ndistribution of subhalos in Milky Way-size halos is consistent with the\nobserved distribution for k_{cut}~50-800 h/Mpc; such models resolve the\nso-called "missing satellite problem".\n