Structure of Dark Matter Halos in Warm Dark Matter models and in models with Long-Lived Charged Massive Particles

摘要

We study the formation of non-linear structures in Warm Dark Matter (WDM)models and in a Long-Lived Charged Massive Particle (CHAMP) model. CHAMPs witha decay lifetime of about 1 yr induce characteristic suppression in the matterpower spectrum at subgalactic scales through acoustic oscillations in thethermal background. We explore structure formation in such a model. We alsostudy three WDM models, where the dark matter particles are produced throughthe following mechanisms: i) WDM particles are produced in the thermalbackground and then kinematically decoupled; ii) WDM particles are fermionsproduced by the decay of thermal heavy bosons; and iii) WDM particles areproduced by the decay of non-relativistic heavy particles. We show that thelinear matter power spectra for the three models are all characterised by thecomoving Jeans scale at the matter-radiation equality. Furthermore, we can alsodescribe the linear matter power spectrum for the Long-Lived CHAMP model interms of a suitably defined characteristic cut-off scale k_{Ch}, similarly tothe WDM models. We perform large cosmological N-body simulations to study thenon-linear growth of structures in these four models. We compare the halo massfunctions, the subhalo mass functions, and the radial distributions of subhalosin simulated Milky Way-size halos. We study the models with k_{cut}=51, 410,820 h/Mpc, and confirm that these statistics are indeed similar between thedifferent WDM models and the Long-Lived CHAMP model. The result suggests thatthe cut-off scale k_{cut} not only characterises the linear power spectra butalso can be used to predict the non-linear clustering properties. The radialdistribution of subhalos in Milky Way-size halos is consistent with theobserved distribution for k_{cut}~50-800 h/Mpc; such models resolve theso-called "missing satellite problem".