On the use of X-ray and gamma-ray telescopes for identifying the origin of electrons and positrons observed by ATIC, Fermi, and PAMELA

TL;DR

This paper explores how X-ray and gamma-ray observations of dwarf spheroidal galaxies can help determine whether high-energy electrons and positrons originate from dark matter or astrophysical sources, considering particle propagation effects.

Contribution

It provides a method to distinguish dark matter from astrophysical sources using gamma-ray and X-ray data, accounting for electron diffusion and halo mass uncertainties.

Findings

Gamma-ray signals may exceed observational limits for certain halo masses.

Electron diffusion can produce detectable X-ray signals with future telescopes.

Uncertainties in halo mass affect the interpretation of gamma-ray observations.

Abstract

X-ray and gamma-ray observations can help understand the origin of the electron and positron signals reported by ATIC, PAMELA, PPB-BETS, and Fermi. It remains unclear whether the observed high-energy electrons and positrons are produced by relic particles, or by some astrophysical sources. To distinguish between the two possibilities, one can compare the electron population in the local neighborhood with that in the dwarf spheroidal galaxies, which are not expected to host as many pulsars and other astrophysical sources. This can be accomplished using X-ray and gamma-ray observations of dwarf spheroidal galaxies. Assuming the signal detected by Fermi and ATIC comes from dark matter and using the inferred dark matter profile of the Draco dwarf spheroidal galaxy as an example, we calculate the photon spectrum produced by electrons via inverse Compton scattering. Since little is known about the magnetic fields in dwarf spheroidal galaxies, we consider the propagation of charged particles with and without diffusion. Extending the analysis of Fermi collaboration for Draco, we find that for a halo mass ~ 1 billion Solar masses, even in the absence of diffusion, the gamma-ray signal would be above the upper limits. This conclusion is subject to uncertainties associated with the halo mass. If dwarf spheroidal galaxies host local magnetic fields, the diffusion of the electrons can result in a signal detectable by future X-ray telescopes.