Destruction of small-scale dark matter clumps in the hierarchical structures and galaxies

Abstract

A mass function of small-scale dark matter clumps is calculated in the standard cosmological scenario with an inflationary-produced primordial fluctuation spectrum and with a hierarchical clustering. We take into account the tidal destruction of clumps at early stages of structure formation starting from a time of clump detachment from the Universe expansion. Only a small fraction of these clumps, ~0.1-0.5%, in each logarithmic mass interval $Δ\log M\sim1$ survives the stage of hierarchical clustering. The surviving clumps can be disrupted further in the galaxies by tidal interactions with stars. We performed the detailed calculations of the tidal destruction of clumps by stars in the Galactic bulge and halo and by the Galactic disk itself. It is shown that the Galactic disc provides the dominant contribution to the tidal destruction of small-scale clumps outside the bulge. The results obtained are crucial for calculations of the dark matter annihilation signal in the Galaxy.