Dark Matter implications of Fermi-LAT measurement of anisotropies in the diffuse gamma-ray background

TL;DR

This paper investigates how anisotropies in the diffuse gamma-ray background, measured by Fermi-LAT, can be used to constrain dark matter properties by comparing observations with cosmological simulation predictions.

Contribution

It provides the first detailed comparison between Fermi-LAT anisotropy measurements and cosmological simulations to derive new constraints on dark matter models.

Findings

Fermi-LAT detected significant anisotropies in gamma-ray background.

Comparison with simulations constrains dark matter annihilation/decay properties.

Results limit certain dark matter candidate parameters.

Abstract

The detailed origin of the diffuse gamma-ray background is still unknown. However, the contribution of unresolved sources is expected to induce small-scale anisotropies in this emission, which may provide a way to identify and constrain the properties of its contributors. Recent studies have predicted the contributions to the angular power spectrum (APS) from extragalactic and galactic dark matter (DM) annihilation or decay. The Fermi-LAT collaboration reported detection of angular power with a significance larger than $3\sigma$ in the energy range from 1 GeV to 10 GeV on 22 months of data [Ackermann et al. 2012]. For these preliminary results the already published Fermi-LAT APS measurements [Ackermann et al. 2012] are compared to the accurate predictions for DM anisotropies from state-of-the-art cosmological simulations as presented in [Fornasa et al. 2013] to derive constraints on different DM candidates.