No abstract

No abstract

It is demonstrated that clusters of galaxies are able to keep cosmic rays for a time exceeding the age of the universe. This phenomenon reveals itself by the production of the di †use Ñux of high-energy gamma and neutrino radiation due to the interaction of the cosmic rays with the intracluster gas. The produced Ñux is determined by the cosmological density of baryons, if a large part of this density is provided ) b , by the intracluster gas. The signal from relic cosmic rays has to be compared with the Ñux produced by the late sources, which can be considered as a background in the search for cosmic-ray production in the past. We calculate this Ñux considering the normal galaxies and active galactic nuclei (AGNs) in the clusters as the sources of cosmic rays. Another potential cosmic-ray source is the shock in the gas accreting to a cluster. We found that this background is relatively high : the di †use Ñuxes produced by relic cosmic rays are of the same order of magnitude that can be expected from AGNs in the clusters. In all cases the predicted di †use gamma-ray Ñux is smaller than the observed one, and the di †use neutrino Ñux can be seen as the small bump at E D 106 GeV over the atmospheric neutrino Ñux. A bright phase in the galaxy evolution can be a source of the relic cosmic rays in clusters, revealing itself by di †use gamma and neutrino radiation. We found that the observation of a signal from the bright phase is better for an individual cluster.

Production of small-scale DM clumps is studied in the standard cosmological scenario with an inflation-produced primeval fluctuation spectrum. Special attention is given to the three following problems: (i) The mass spectrum of small-scale clumps with M 10 3 M⊙ is calculated with tidal destruction of the clumps taken into account within the hierarchical model of clump structure. Only 0.1 -0.5% of small clumps survive the stage of tidal destruction in each logarithmic mass interval ∆ ln M ∼ 1. (ii) The mass distribution of clumps has a cutoff at Mmin due to diffusion of DM particles out of a fluctuation and free streaming at later stage. Mmin is a model dependent quantity. In the case the neutralino, considered as a pure bino, is a DM particle, Mmin ∼ 10 −8 M⊙. (iii) The evolution of density profile in a DM clump does not result in the singularity because of formation of the core under influence of tidal interaction. The radius of the core is Rc ∼ 0.1R, where R is radius of the clump. The applications for annihilation of DM particles in the Galactic halo are studied. The number density of clumps as a function of their mass, radius and distance to the Galactic center is presented. The enhancement of annihilation signal due to clumpiness, valid for arbitrary DM particles, is calculated. In spite of small survival probability, the global annihilation signal in most cases is dominated by clumps. For observationally preferable value of index of primeval fluctuation spectrum np ≈ 1, the enhancement of annihilation signal is described by factor 2 -5 for different density profiles in a clump.PACS numbers: 12.60. Jv, 95.35.+d, 98.35.Gi