Dark Matter Annihilation Of Dark Halo Density Profile

Structure formation model based on the cold dark matter (CDM) theory and the nearly scale-invariant primordial perturbation has successfully explained the main features of observational properties of the large scale structure and galaxies. It is considered to be the basis of the Standard Model of modern cosmology, although there still are some challenges on small scale. While current high resolution simulations based on the CDM model, for instance, predict a universal density profile of dark matter halos with singular density cusps in the centers, the observations of rotation curves of dwarf galaxies imply that halos show flat cores there. This discrepancy leads to some work about modification of standard CDM model.In the present thesis, the dark matter annihilation is discussed in detail. Taking the widely adopted density profile, i.e., NFW profile, as illustration, the phenomenological model of dark matter annihilation is established to investigate the effect on the evolution of dark halo density profile.The main conclusions are summarized as follows.1. The annihilation of dark matter can result a flat core in the inner region of the dark matter halo, which is consistent with observations;2. There are two free parameters in the model, i.e., the mass of dark matter particle md mand the power index of boost factorα.Taking the observed rotation curves of low surface brightness galaxies and local dark matter density as constraints, it is found that the favored ranges of these two parameter are 100Gev≤mdm≤10Tev and 1.5≤α≤1.8, respectively;3. The predicted flux of gamma rays produced by dark matter annihilation adopting the specific particle dark matter model (neutralinos) is estimated and compared with the current observations of high energy cosmic rays. It is found that the flux predicted in the model far exceeds the upper limits of current observations. This requires another appropriate particle dark matter models for the discrepancy.