Modelling the flux distribution function of the extragalactic gamma-ray background from dark matter annihilation

Journal Article · Tue Sep 01 00:00:00 EDT 2015 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2015/09/027· OSTI ID:22525380

Feyereisen, Michael R.; Ando, Shin'ichiro ^[1]

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1. GRAPPA Institute, University of Amsterdam, Science Park 904, Amsterdam, 1098 XH The Netherlands (Netherlands)

The one-point function (i.e., the isotropic flux distribution) is a complementary method to (anisotropic) two-point correlations in searches for a gamma-ray dark matter annihilation signature. Using analytical models of structure formation and dark matter halo properties, we compute the gamma-ray flux distribution due to annihilations in extragalactic dark matter halos, as it would be observed by the Fermi Large Area Telescope. Combining the central limit theorem and Monte Carlo sampling, we show that the flux distribution takes the form of a narrow Gaussian of 'diffuse' light, with an 'unresolved point source' power-law tail as a result of bright halos. We argue that this background due to dark matter constitutes an irreducible and significant background component for point-source annihilation searches with galaxy clusters and dwarf spheroidal galaxies, modifying the predicted signal-to-noise ratio. A study of astrophysical backgrounds to this signal reveals that the shape of the total gamma-ray flux distribution is very sensitive to the contribution of a dark matter component, allowing us to forecast promising one-point upper limits on the annihilation cross-section. We show that by using the flux distribution at only one energy bin, one can probe the canonical cross-section required for explaining the relic density, for dark matter of masses around tens of GeV.

• OSTI ID: 22525380
• Journal Information: Journal of Cosmology and Astroparticle Physics, Vol. 2015, Issue 09; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ANISOTROPY
ANNIHILATION
ASTROPHYSICS
CORRELATIONS
CROSS SECTIONS
DENSITY
DISTRIBUTION FUNCTIONS
GALAXIES
GALAXY CLUSTERS
GAMMA RADIATION
GEV RANGE
MASS
MONTE CARLO METHOD
NONLUMINOUS MATTER
POINT SOURCES
PROBES
SIGNAL-TO-NOISE RATIO
TELESCOPES
VISIBLE RADIATION