Diffuse Galactic Gamma Rays from Shock-Accelerated Cosmic Rays

Abstract

A shock-accelerated particle flux \propto p^-s, where p is the particle momentum, follows from simple theoretical considerations of cosmic-ray acceleration at nonrelativistic shocks followed by rigidity-dependent escape into the Galactic halo. A flux of shock-accelerated cosmic-ray protons with s ~ 2.8 provides an adequate fit to the Fermi-LAT gamma-ray emission spectra of high-latitude and molecular cloud gas when uncertainties in nuclear production models are considered. A break in the spectrum of cosmic-ray protons claimed by Neronov, Semikoz, & Taylor (PRL, 108, 051105, 2012) when fitting the gamma-ray spectra of high-latitude molecular clouds is a consequence of using a cosmic-ray proton flux described by a power law in kinetic energy.

Version to correspond to published letter in PRL; corrected Fig. 2

References in corpus (8)

• Measurement of the Cosmic Ray e+ plus e- spectrum from 20 GeV to 1 TeV with the Fermi Large Area Telescope
• The Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived From First-Year Fermi Large Area Telescope Data
• Parameterization of Gamma, e^+/- and Neutrino Spectra Produced by p-p Interaction in Astronomical Environment
• The cosmic-ray electron flux measured by the PAMELA experiment between 1 and 625 GeV
• Spectral breaks as a signature of cosmic ray induced turbulence in the Galaxy
• Parameterization of the Angular Distribution of Gamma Rays Produced by p-p Interaction in Astronomical Environment
• Non-thermal emission from old supernova remnants
• Revised production cross-section of gamma-rays in p-p collisions with LHC data for the study of TeV gamma-ray astronomy

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• Cosmic ray spectrum in the local Galaxy
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• Fermi LAT Observation of Supernova Remnant HB9
• Early-time gamma-ray constraints on cosmic-ray acceleration in the core-collapse SN 2023ixf with the Fermi Large Area Telescope
• Determining the Spectrum of Cosmic Rays in Interstellar Space from the Diffuse Galactic Gamma-Ray Emissivity
• Energy dependence of the knee in the cosmic ray spectrum across the Milky Way
• Gamma-ray signature of superluminous supernovae: Fermi-LAT GeV detection of SN 2017egm and evidence of a central engine
• Impact of Fermi-LAT and AMS-02 results on cosmic-ray astrophysics