Prompt cusps and the dark matter annihilation signal

Abstract

As the first dark matter objects gravitationally condense, a density cusp forms immediately at every initial density maximum. Numerical simulations and theoretical arguments suggest that these prompt cusps can survive until the present day. We show that if dark matter is a thermally produced weakly interacting massive particle, many thousands of prompt cusps with individual masses similar to that of the Earth may be present in every solar mass of dark matter. This radically alters predictions for the amount and spatial distribution of dark matter annihilation radiation. The annihilation rate is boosted by at least an order of magnitude compared to previous predictions, both in the cosmological average and within galaxy-scale halos. Moreover, the signal is predominantly boosted outside of the centers of galactic halos, so alternative targets become significantly more attractive for indirect-detection searches. For example, prompt cusps present new opportunities to test the dark matter interpretation of the Galactic Center gamma-ray excess by searching for similar spectral signatures in the isotropic gamma-ray background and large-scale cosmic structure.

26 pages, 12 figures; accepted for publication in JCAP. Prompt cusp survival analysis slightly altered; various clarifications made

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• 21-cm Constraints on Dark Matter Annihilation after an Early Matter-Dominated Era
• The influence of baryons on low-mass haloes
• Limits on Early Matter Domination from the Isotropic Gamma-Ray Background
• Collisionless relaxation from near equilibrium configurations: Linear theory and application to tidal stripping
• The cusp-halo relation
• Structure Formation with Warm White Noise: Effects of Finite Number Density and Velocity Dispersion in Particle and Wave Dark Matter
• Prospects for annihilating dark matter from M31 and M33 observations with the Cherenkov Telescope Array
• Can WIMPs Survive the Legacy of a Magnetised Early Universe?
• New insights on low-mass dark matter subhalo tidal tracks via numerical simulations
• Excursion Sets with a "Perfect" Collapse Model
• Post-collapse Lagrangian perturbation theory in three dimensions
• Role of prompt cusps in driving the core collapse of SIDM halos
• Prompt cusps in hierarchical dark matter halos: Implications for annihilation boost