Distinguishing Dark Matter from Unresolved Point Sources in the Inner Galaxy with Photon Statistics

TL;DR

This paper explores whether photon statistics, specifically the flux PDF, can differentiate between dark matter and unresolved point sources like millisecond pulsars as the origin of gamma-ray excess in the Inner Galaxy.

Contribution

It introduces a novel statistical approach using the flux PDF to distinguish dark matter signals from unresolved point sources in gamma-ray data.

Findings

Flux PDF can differentiate between dark matter and point-source models.

Bayesian analysis favors unresolved millisecond pulsars as the source.

Method provides a new tool for analyzing gamma-ray excess origins.

Abstract

Data from the Fermi Large Area Telescope suggests that there is an extended excess of GeV gamma-ray photons in the Inner Galaxy. Identifying potential astrophysical sources that contribute to this excess is an important step in verifying whether the signal originates from annihilating dark matter. In this paper, we focus on the potential contribution of unresolved point sources, such as millisecond pulsars (MSPs). We propose that the statistics of the photons---in particular, the flux probability density function (PDF) of the photon counts below the point-source detection threshold---can potentially distinguish between the dark-matter and point-source interpretations. We calculate the flux PDF via the method of generating functions for these two models of the excess. Working in the framework of Bayesian model comparison, we then demonstrate that the flux PDF can potentially provide evidence for an unresolved MSP-like point-source population.