Extragalactic gamma-ray signal from dark matter annihilation: an appraisal

Abstract

We re-evaluate the extragalactic gamma-ray flux prediction from dark matter annihilation in the approach of integrating over the nonlinear matter power spectrum, extrapolated to the free-streaming scale. We provide an estimate of the uncertainty based entirely on available N-body simulation results and minimal theoretical assumptions. We illustrate how an improvement in the simulation resolution, exemplified by the comparison between the Millennium and Millennium II simulations, affects our estimate of the flux uncertainty and we provide a "best guess" value for the flux multiplier, based on the assumption of stable clustering for the dark matter perturbations described as a collision-less fluid. We achieve results comparable to traditional Halo Model calculations, but with a much simpler procedure and a more general approach, as it relies only on one, directly measurable quantity. In addition we discuss the extension of our calculation to include baryonic effects as modeled in hydrodynamical cosmological simulations and other possible sources of uncertainty that would in turn affect indirect dark matter signals. Upper limit on the integrated power spectrum from supernovae lensing magnification are also derived and compared with theoretical expectations.

20 pages, 9 figures, 1 table. Updated to match the published version. New material and figures added, conclusions unchanged

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• The nature of the Diffuse Gamma-Ray Background
• Composition of the Fermi-LAT isotropic gamma-ray background intensity: Emission from extragalactic point sources and dark matter annihilations
• IceCube events and decaying dark matter: hints and constraints
• WIMP searches with gamma rays in the Fermi era: challenges, methods and results
• Low energy IceCube data and a possible Dark Matter related excess
• Update on decaying and annihilating heavy dark matter with the 6-year IceCube HESE data
• Realistic estimation for the detectability of dark matter sub-halos with Fermi-LAT
• Confronting Galactic and Extragalactic $\gamma$-ray observed by Fermi-LAT with Annihilating Dark Matter in Inert Higgs Doublet Model
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• The role of the eROSITA all-sky survey in searches for sterile neutrino dark matter
• Universal clustering of dark matter in phase space
• Extragalactic diffuse gamma-rays from dark matter annihilation: revised prediction and full modelling uncertainties
• Future sensitivity of neutrino telescopes to dark matter annihilations from the cosmic diffuse neutrino signal
• Impacts of new small-scale N-body simulations on dark matter annihilations constrained from cosmological 21cm line observations
• Confronting recent AMS-02 positron fraction and Fermi-LAT Extragalactic Gamma-Ray Background measurements with gravitino dark matter
• Minihalos as probes of the inflationary spectrum: accurate boost factor calculation and new CMB constraints
• Addressing $\gamma$-ray emissions from dark matter annihilations in 45 milky way satellite galaxies and in extragalactic sources with particle dark matter models
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• Influence of the deviation of the matter power spectrum at small scales on the global 21-cm signal at cosmic dawn
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