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

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 with a decay lifetime of about 1 yr induce characteristic suppression in the matter power spectrum at subgalactic scales through acoustic oscillations in the thermal background. We explore structure formation in such a model. We also study three WDM models, where the dark matter particles are produced through the following mechanisms: i) WDM particles are produced in the thermal background and then kinematically decoupled; ii) WDM particles are fermions produced by the decay of thermal heavy bosons; and iii) WDM particles are produced by the decay of non-relativistic heavy particles. We show that the linear matter power spectra for the three models are all characterised by the comoving Jeans scale at the matter-radiation equality. Furthermore, we can also describe the linear matter power spectrum for the long-lived CHAMP model in terms of a suitably defined characteristic cut-off scale k(Ch), similarly to the WDM models. We perform large cosmological N-body simulations to study the non-linear growth of structures in these four models. We compare the halo mass functions, the subhalo mass functions, and the radial distributions of subhalos in simulated Milky Way-size halos. For the characteristic cut-off scale k(cut) = 51 h Mpc(-1), the subhalo abundance (similar to 10(9) M-sun) is suppressed by a factor of similar to 10 compared with the standard Lambda CDM model. We then study the models with k(cut) similar or equal to 51, 410, 820 h Mpc(-1), and confirm that the halo and the subhalo abundances and the radial distributions of subhalos are indeed similar between the different WDM models and the long-lived CHAMP model. The result suggests that the cut-off scale k(cut) not only characterises the linear power spectra but also can be used to predict the non-linear clustering properties. The radial distribution of subhalos in Milky Way-size halos is consistent with the observed distribution for k(cut) similar to 50 - 800 h Mpc(-1); such models resolve the so-called missing satellite problem.