Clumpy cold dark matter

Abstract

Clumpiness is likely to be generic to cold dark matter cosmologies. We consider cold dark matter models with cosmic strings and textures appropriate for galaxy formation. CDM clumps with a density of approximately 10(7) M. pc-3 are generated at redshift approximately z(eq) and a sizable fraction of them may survive to today. The most numerous clumps should have dense cores of mass approximately 10(-2) (1 GeV/M(x))3/2 M., where M(x) is the mass of the dark matter particle and might contain up to 10(-3) of the CDM mass. Even in canonical, unseeded cold dark matter models, there is also likely to be clumpiness, developing when the first rare fluctuations go non-linear, and surviving on scales of up to 10(8) M. in galaxy halos. Observable implications include possible dark matter cores in globular clusters, and in galactic nuclei. The enhanced annihilation rate in clumps can lead to a significant contribution to the diffuse gamma-ray background, as well as emission from the Galactic center. Results from terrestrial dark matter detection experiments might be significantly affected by clumpiness in the Galactic halo.