Multi-messenger constraints on the annihilating dark matter interpretation of the positron excess

TL;DR

This study uses multi-messenger astrophysical data to test dark matter annihilation models as an explanation for the positron excess, finding that current models are inconsistent with observations across multiple wavelengths.

Contribution

It introduces a multi-messenger analysis framework and star plots to simultaneously compare dark matter model predictions with diverse astrophysical constraints.

Findings

Dark matter models cannot explain positron excess without conflicting with gamma-ray, radio, or antiproton data.

Standard dark matter distribution assumptions limit the viability of annihilation explanations.

Multi-messenger constraints strongly challenge the dark matter interpretation of the positron excess.

Abstract

The rise in the energy spectrum of the positron ratio, observed by the PAMELA satellite above 10 GeV, and other cosmic ray measurements, have been interpreted as a possible signature of Dark Matter annihilation in the Galaxy. However, the large number of free parameters, and the large astrophysical uncertainties, make it difficult to do conclusive statements about the viability of this scenario. Here, we perform a multi-wavelength, multi-messenger analysis, that combines in a consistent way the constraints arising from different astrophysical observations. We show that if standard assumptions are made for the distribution of Dark Matter (we build models on the recent Via Lactea II and Aquarius simulations) and the propagation of cosmic rays, current DM models cannot explain the observed positron flux without exceeding the observed fluxes of antiprotons or gamma-ray and radio photons. To visualize the multi-messenger constraints, we introduce "star plots", a graphical method that allows to show in the same plot theoretical predictions and observational constraints for different messengers and wavelengths.