Pulsars versus Dark Matter Interpretation of ATIC/PAMELA

TL;DR

This paper compares pulsar and dark matter sources for high-energy electrons and positrons, analyzing flux contributions, spectral features, and implications for recent cosmic ray data from ATIC, PAMELA, Fermi, and HESS.

Contribution

It provides a detailed analysis of pulsar and dark matter contributions to cosmic ray electrons and positrons, highlighting spectral features and their implications for interpreting recent data.

Findings

High-energy flux dominated by nearby pulsars, producing spectral bumps.

Absence of spectral features suggests dark matter or suppressed pulsar fluctuations.

Features can be smeared by spatial energy loss variations during propagation.

Abstract

In this paper, we study the flux of electrons and positrons injected by pulsars and by annihilating or decaying dark matter in the context of recent ATIC, PAMELA, Fermi, and HESS data. We review the flux from a single pulsar and derive the flux from a distribution of pulsars. We point out that the particle acceleration in the pulsar magnetosphere is insufficient to explain the observed excess of electrons and positrons with energy E ~ 1 TeV and one has to take into account an additional acceleration of electrons at the termination shock between the pulsar and its wind nebula. We show that at energies less than a few hundred GeV, the flux from a continuous distribution of pulsars provides a good approximation to the expected flux from pulsars in the Australia Telescope National Facility (ATNF) catalog. At higher energies, we demonstrate that the electron/positron flux measured at the Earth will be dominated by a few young nearby pulsars, and therefore the spectrum would contain bumplike features. We argue that the presence of such features at high energies would strongly suggest a pulsar origin of the anomalous contribution to electron and positron fluxes. The absence of features either points to a dark matter origin or constrains pulsar models in such a way that the fluctuations are suppressed. Also we derive that the features can be partially smeared due to spatial variation of the energy losses during propagation.