2,527 research outputs found
Gamma-Ray Constraints on Neutralino Dark Matter Clumps in the Galactic Halo
According to high resolution cold dark matter (CDM) simulations, large
virialized halos are formed through the constant merging of smaller halos
formed at earlier times. In particular, the halo of our Galaxy may have
hundreds of dark matter clumps. The annihilation of dark matter particles such
as the neutralino in these clumps generates -ray fluxes that can
potentially be detected by future experiments such as GLAST. We find that,
depending on the parameters of the clump density profile and on the
distribution of clumps in the Galactic halo, the contribution to the diffuse
-ray background from clumps can constrain the properties of neutralinos
such as the mass and annihilation cross section. We model the density profile
of clumps by three representative dark matter profiles: singular isothermal
spheres (SIS), Moore profiles, and Navarro, Frenk and White (NFW) density
profiles and calculate the spectrum and angular distribution in the sky of the
-ray flux due to neutralino annihilation in the clumpy halo of the
Galaxy. The calculations are carried out in the context of two different
scenarios for the distribution of clumps in the Galaxy and their
concentrations, which result in very different conclusions.Comment: 24 pages, 7 ps fig
Non linear particle acceleration at non-relativistic shock waves in the presence of self-generated turbulence
Particle acceleration at astrophysical shocks may be very efficient if
magnetic scattering is self-generated by the same particles. This nonlinear
process adds to the nonlinear modification of the shock due to the dynamical
reaction of the accelerated particles on the shock. Building on a previous
general solution of the problem of particle acceleration with arbitrary
diffusion coefficients (Amato & Blasi, 2005), we present here the first
semi-analytical calculation of particle acceleration with both effects taken
into account at the same time: charged particles are accelerated in the
background of Alfven waves that they generate due to the streaming instability,
and modify the dynamics of the plasma in the shock vicinity.Comment: submitted to MNRA
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