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Characterization of dark-matter-induced anisotropies in the diffuse gamma-ray background.

Fornasa, M. and Zavala, J. and Sánchez-Conde, M.A. and Siegal-Gaskins, J.M. and Delahaye, T. and Prada, F. and Vogelsberger, M. and Zandanel, F. and Frenk, C.S. (2013) 'Characterization of dark-matter-induced anisotropies in the diffuse gamma-ray background.', Monthly notices of the Royal Astronomical Society., 429 (2). pp. 1529-1553.


The Fermi-LAT collaboration has recently reported the detection of angular power above the photon noise level in the diffuse gamma-ray background between 1 and 50 GeV. Such signal can be used to constrain a possible contribution from dark matter (DM) induced photons. We estimate the intensity and features of the angular power spectrum (APS) of this potential DM signal, for both decaying and annihilating DM candidates, by constructing template all-sky gamma-ray maps for the emission produced in the galactic halo and its substructures, as well as in extragalactic (sub)haloes. The DM distribution is given by state-of-the-art N-body simulations of cosmic structure formation, namely Millennium-II for extragalactic (sub)haloes, and Aquarius for the galactic halo and its subhaloes. We use a hybrid method of extrapolation to account for (sub)structures that are below the resolution limit of the simulations, allowing us to estimate the total emission all the way down to the minimal self-bound halo mass. We describe in detail the features appearing in the APS of our template maps and we estimate the effect of various uncertainties such as the value of the minimal halo mass, the fraction of substructures hosted in a halo and the shape of the DM density profile. Our results indicate that the fluctuation APS of the DM-induced emission is of the same order as the Fermi-LAT APS, suggesting that one can constrain this hypothetical emission from the comparison with the measured anisotropy. We also quantify the uncertainties affecting our results, finding ‘theoretical error bands’ spanning more than two orders of magnitude and dominated (for a given particle physics model) by our lack of knowledge of the abundance of low-mass (sub)haloes.

Item Type:Article
Keywords:Astroparticle physics, Methods: numerical, Cosmology: dark matter, Gamma-rays: diffuse background.
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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2013 The Authors Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.
Date accepted:No date available
Date deposited:27 June 2014
Date of first online publication:February 2013
Date first made open access:No date available

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