Fermi Gamma-ray Haze via Dark Matter and Millisecond Pulsars

Abstract

We study possible astrophysical and dark matter (DM) explanations for the Fermi gamma-ray haze in the Milky Way halo. As representatives of various DM models, we consider DM particles annihilating into W+W-, b-bbar, and e+e-. In the first two cases, the prompt gamma-ray emission from DM annihilations is significant or even dominant at E > 10 GeV, while inverse Compton scattering (ICS) from annihilating DM products is insignificant. For the e+e- annihilation mode, we require a boost factor of order 100 to get significant contribution to the gamma-ray haze from ICS photons. Possible astrophysical sources of high energy particles at high latitudes include type Ia supernovae (SNe) and millisecond pulsars (MSPs). Based on our current understanding of Ia SNe rates, they do not contribute significantly to gamma-ray flux in the halo of the Milky Way. As the MSP population in the stellar halo of the Milky Way is not well constrained, MSPs may be a viable source of gamma-rays at high latitudes provided that there are ~ 20 000 - 60 000 of MSPs in the Milky Way stellar halo. In this case, pulsed gamma-ray emission from MSPs can contribute to gamma-rays around few GeV's while the ICS photons from MSP electrons and positrons may be significant at all energies in the gamma-ray haze. The plausibility of such a population of MSPs is discussed. Consistency with the Wilkinson Microwave Anisotropy Probe (WMAP) microwave haze requires that either a significant fraction of MSP spin-down energy is converted into e+e- flux or the DM annihilates predominantly into leptons with a boost factor of order 100.

18 pages, 1 table, 5 figures; v2: references and a few discussions added, v3: minor changes

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Cited by in corpus (20)

• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• On The Origin Of The Gamma Rays From The Galactic Center
• Pulsars Cannot Account for the Inner Galaxy's GeV Excess
• Sensitivity Projections for Dark Matter Searches with the Fermi Large Area Telescope
• Wild at Heart:-The Particle Astrophysics of the Galactic Centre
• The Galactic Center GeV Excess from a Series of Leptonic Cosmic-Ray Outbursts
• Non-Thermal Insights on Mass and Energy Flows Through the Galactic Centre and into the Fermi Bubbles
• Statistics of gamma-ray point sources below the Fermi detection limit
• Numerical study of Cosmic Ray Diffusion in MHD turbulence
• Extracting limits on Dark Matter annihilation from gamma-ray observations towards dwarf spheroidal galaxies
• Dissecting the Gamma-Ray Background in Search of Dark Matter
• The Fermi Gamma-Ray Haze from Dark Matter Annihilations and Anisotropic Diffusion
• Constraints on dark matter annihilations from diffuse gamma-ray emission in the Galaxy
• High Energy Neutrinos from the Fermi Bubbles
• Detection Potential of the KM3NeT Detector for High-Energy Neutrinos from the Fermi Bubbles
• Diffuse Galactic Gamma Rays at intermediate and high latitudes. I. Constraints on the ISM properties
• Dark matter implications of the WMAP-Planck Haze
• Searching for High Energy Neutrino counterpart signals; The case of the Fermi Bubbles signal and of Dark Matter annihilation in the inner Galaxy
• Extracting the unresolved pulsar contribution to the gamma-ray background
• Spherical harmonics analysis of Fermi gamma-ray data and the Galactic dark matter halo