THE ORIGIN OF THE EXTRAGALACTIC GAMMA-RAY BACKGROUND AND IMPLICATIONS FOR DARK MATTER ANNIHILATION
2015 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, Vol. 800, no 2, L27Article in journal (Refereed) Published
The origin of the extragalactic.-ray background (EGB) has been debated for some time. The EGB comprises the.-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 similar to 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.
Place, publisher, year, edition, pages
2015. Vol. 800, no 2, L27
cosmology: observations, dark matter, galaxies: active, galaxies: jets, gamma rays: diffuse background, surveys
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-115675DOI: 10.1088/2041-8205/800/2/L27ISI: 000349692900008OAI: oai:DiVA.org:su-115675DiVA: diva2:799811