Primary versus secondary leptons in the EGRET supernova remnants

Marco Fatuzzo, Fulvio Melia

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The EGRET supernova remnants (SNRs) are all expanding into nearby dense molecular clouds, powering a shock at the interface where protons and electrons accelerate to relativistic energies. A viable mechanism for the emission of γ-rays in these sources is the decay of neutral pions created in collisions between the relativistic hadrons and protons in the ambient medium. But neutral pion decay alone cannot reproduce the whole high-energy spectrum, particularly below 100 MeV. A pion decay scenario thus requires a lepton population to fill in the lower part of the spectrum via bremsstrahlung emission. This population, however, is constrained by the SNR radio spectrum. Taking our cue from the behavior of Sgr A East, an energetic EGRET SNR at the Galactic center, we here examine the role played in these sources by secondary leptons - electrons and positrons produced in proton-proton scattering events and the ensuing particle cascades. We show that, while secondary leptons cannot account for the γ-rays below 100 MeV, they can account for the hard radio spectra observed from the EGRET SNRs. Thus, it appears that both primary and secondary leptons may be important contributors to the overall broadband emission from these sources, but if so, they must radiate most of their energy in different parts of the SNR-cloud environment. We show that shock acceleration in dense cores being overtaken by the expanding SNR shell can naturally lead to such a scenario.

Original languageEnglish (US)
Pages (from-to)321-331
Number of pages11
JournalAstrophysical Journal
Volume630
Issue number1 I
DOIs
StatePublished - Sep 1 2005

Fingerprint

supernova remnants
leptons
radio spectra
pions
radio
energy
electron
protons
rays
decay
shock
energetics
collision
scattering
cues
proton scattering
shell
molecular clouds
hadrons
bremsstrahlung

Keywords

  • Acceleration of particles
  • Cosmic rays
  • Galaxies: nuclei
  • Galaxy: center gamma rays: theory
  • Radiation mechanisms: nonthermal
  • Supernova remnants

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Primary versus secondary leptons in the EGRET supernova remnants. / Fatuzzo, Marco; Melia, Fulvio.

In: Astrophysical Journal, Vol. 630, No. 1 I, 01.09.2005, p. 321-331.

Research output: Contribution to journalArticle

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