THE ORIGIN OF THE EXTRAGALACTIC GAMMA-RAY BACKGROUND AND IMPLICATIONS FOR DARK MATTER ANNIHILATION

By M. Ajello, D. Gasparrini, M. Sánchez-Conde, G. Zaharijas, M. Gustafsson, J. Cohen-Tanugi, C. Dermer, Y. Inoue, D. Hartmann, M. Ackermann and 5 more. 2015

194 citations recorded by the source corpus.

The origin of the extragalactic γ-ray background (EGB) has been debated for some time. The EGB comprises the γ-ray emission from resolved and unresolved extragalactic sources, such as blazars, star-forming galaxies, and radio galaxies, as well as radiation from truly diffuse processes. This Letter focuses on the blazar source class, the most numerous detected population, and presents an updated luminosity function and spectral energy distribution model consistent with the blazar observations performed by the Fermi-Large Area Telescope (LAT). We show that blazars account for 50 − 11 + 12 ?> % of the EGB photons (>0.1 GeV), and that Fermi-LAT has already resolved ∼70% of this contribution. Blazars, and in particular hard-spectrum sources such as BL Lacs, are responsible for most of the EGB emission above 100 GeV. We find that the extragalactic background light, which attenuates blazars’ high-energy emission, is responsible for the high-energy cutoff observed in the EGB spectrum. Finally, we show that blazars, star-forming galaxies, and radio galaxies can naturally account for the amplitude and spectral shape of the background in the 0.1–820 GeV range, leaving only modest room for other contributions. This allows us to set competitive constraints on the dark matter annihilation cross section.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/75c1a6706004bd93076553d502608022d83a374e

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In Nuclear and High Energy Physics

Citations in the corpus

Sensitivity projections for dark matter searches with the Fermi large area telescope (2016, methodology): “[77]; additional details are available there; reproduced by permission of the AAS.”
Limits on dark matter annihilation signals from the Fermi LAT 4-year measurement of the isotropic gamma-ray background (2015, methodology): “Indeed, this is what is obtained in a companion work [96], where unresolved astrophysical source populations were modeled and used to set new DM limits on DM annihilation cross sections.”
Active galactic nuclei: what’s in a name? (2017, methodology): “This includes 415 FSRQs (all of the LSP type), 657 BL Lacs (mostly of the HSP type), and 402 blazars of uncertain type (assumed to be blazars because of their radio to γ -ray SED but with no optical spectrum yet available to classify them as FSRQs or BL Lacs).”