Constraining Galactic dark matter with gamma-ray pixel counts statistics

TL;DR

This paper uses gamma-ray photon count statistics from Fermi-LAT data to resolve extragalactic point sources, decompose the diffuse background, and set new constraints on dark matter annihilation cross sections.

Contribution

It introduces a novel application of 1-point photon count statistics to simultaneously analyze point sources, diffuse background, and dark matter signals in gamma-ray data.

Findings

Resolved extragalactic point source populations.

Decomposed the isotropic gamma-ray background.

Set competitive upper bounds on dark matter annihilation cross section.

Abstract

Gamma-ray searches for new physics such as dark matter are often driven by investigating the composition of the extragalactic gamma-ray background (EGB). Classic approaches to EGB decomposition manifest in resolving individual point sources and dissecting the intensity spectrum of the remaining unresolved component. Furthermore, statistical methods have recently been proven to outperform the sensitivity of classic source detection algorithms in finding point-source populations in the unresolved flux regime. In this article, we employ the 1-point photon count statistics of eight years of Fermi-LAT data to resolve the population of extragalactic point sources and to decompose the diffuse isotropic background contribution for Galactic latitudes |b|>30 deg. We use three adjacent energy bins between 1 and 10 GeV. For the first time, we extend the analysis to incorporate a potential contribution from annihilating dark matter smoothly distributed in the Galaxy. We investigate the sensitivity reach of 1-point statistics for constraining the thermally-averaged self-annihilation cross section <\sigma v> of dark matter, using different template models for the Galactic foreground emission. Given the official Fermi-LAT interstellar emission model, we set upper bounds on the DM self-annihilation cross section <\sigma v> that are comparable with the constraints obtained by other indirect detection methods, in particular by the stacking analysis of several dwarf spheroidal galaxies.