Neutralino Gamma-ray Signals from Accreting Halo Dark Matter

Abstract: There is mounting evidence that a self-consistent model for particle cold dark matter has to take into consideration spatial inhomogeneities on sub-galactic scales seen, for instance, in high-resolution N-body simulations of structure formation. Also in more idealized, analytic models, there appear density enhancements in certain regions of the halo. We use the results from a recent N-body simulation of the Milky Way halo and investigate the gamma-ray flux which would be produced when a specific dark matter candidate, the neutralino, annihilates in regions of enhanced density. The clumpiness found on all scales in the simulation results in very strong gamma-ray signals which seem to already rule out some regions of the supersymmetric parameter space, and would be further probed by upcoming experiments, such as the GLAST gamma-ray satellite. As an orthogonal model of structure formation, we also consider Sikivie's simple infall model of dark matter which predicts that there should exist continuous regions of enhanced density, caustic rings, in the dark matter halo of the Milky Way. We find, however, that the gamma-ray signal from caustic rings is generally too small to be detectable.