Compact Halo around the Sun Accreted after Dark Matter Dissipative Self Interaction

Abstract

If dark matter particle can be decelerated due to its dissipative self scattering, except for sinking at the galaxy scale to speed up structure formation, it can also be accreted onto local celestial bodies such as the Sun, forming a compact halo. With some simplified assumptions we develop the Boltzmann equation set based on the partition function of the elliptical orbits, and numerically solve it for the accretion process. We find that the orbited dark matter particles will form a halo around the Sun, with the density profile well fitted to be proportional to $r^{-1.6}$ in a wide range of radius. While around the earth such local halo contribution is always several orders below the galactic component, in a very small region centered around the Sun the sunk dark matter particles can lead to a halo density several orders larger than the background galactic component, in particular in the parameter region of small deceleration speed and large cross section, which is still consistent with current constraints. Such potential dark matter local halo with significantly enhanced density will be a very interesting source for dark matter indirect detection if the corresponding channel exists, we discuss the possibility of the gamma-ray spectrum in the solar direction in some detail as an example.