Theoretical Interpretation of Pass 8 Fermi-LAT e+ + e− Data

2017/03/31 by Mattia Di Mauro, Silvia Manconi, Andrea Vittino +22
Physics and Astronomy · #Astrophysics #Astrophysics and Cosmic Phenomena #Cosmic ray #Dark Matter and Cosmic Phenomena #Electron #Fermi Gamma-ray Space Telescope #Flux (metallurgy) #Galaxy #Interstellar medium #Nuclear physics #Particle Detector Development and Performance #Physics #Population #Positron #Pulsar #Supernova #Supernova remnant #Vela #astro-ph.HE

paper · pdf · doi:10.3847/1538-4357/aa8225

15 pages, 12 figures. The Astrophysical Journal, Volume 845, Number 2

openalex publication_date 2017/08/17 · openalex created_date 2019/06/27 · arxiv created 2020/11/12 · arxiv updated 2020/11/13 · openalex updated_date 2026/08/06

Abstract

Abstract The flux of positrons and electrons ( e + + e − ) has been measured by the Fermi Large Area Telescope (LAT) in the energy range between 7 GeV and 2 TeV. We discuss a number of interpretations of Pass 8 Fermi -LAT e + + e − spectrum, combining electron and positron emission from supernova remnants (SNRs) and pulsar wind nebulae (PWNe), or produced by the collision of cosmic rays (CRs) with the interstellar medium. We find that the Fermi -LAT spectrum is compatible with the sum of electrons from a smooth SNR population, positrons from cataloged PWNe, and a secondary component. If we include in our analysis constraints from the AMS-02 positron spectrum, we obtain a slightly worse fit to the e + + e − Fermi -LAT spectrum, depending on the propagation model. As an additional scenario, we replace the smooth SNR component within 0.7 kpc with the individual sources found in Green’s catalog of Galactic SNRs. We find that separate consideration of far and near sources helps to reproduce the e + + e − Fermi -LAT spectrum. However, we show that the fit degrades when the radio constraints on the positron emission from Vela SNR (which is the main contributor at high energies) are taken into account. We find that a break in the power-law injection spectrum at about 100 GeV can also reproduce the measured e + + e − spectrum and, among the CR propagation models that we consider, no reasonable break of the power-law dependence of the diffusion coefficient can modify the electron flux enough to reproduce the observed shape.

Citations

• AMS-02 Results Support the Secondary Origin of Cosmic Ray Positrons
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• OBSERVATIONS OF THE SHELL-TYPE SUPERNOVA REMNANT CASSIOPEIA A AT TeV ENERGIES WITH VERITAS
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• Cosmic-ray propagation with DRAGON2: I. numerical solver and astrophysical ingredients
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