Determining the Spectrum of Cosmic Rays in Interstellar Space from the Diffuse Galactic Gamma-Ray Emissivity

Abstract

More than 90% of the Galactic gas-related gamma-ray emissivity above 1 GeV is attributed to the decay of neutral pions formed in collisions between cosmic rays and interstellar matter, with lepton-induced processes becoming increasingly important below 1 GeV. Given the high-quality measurements of the gamma-ray emissivity of local interstellar gas between ~50 MeV and ~4 GeV obtained with the Large Area Telescope on board the Fermi space observatory, it is timely to re-investigate this topic in detail, including the hadronic production mechanisms. The emissivity spectrum will allow the interstellar cosmic-ray spectrum to be determined reliably, providing a reference for origin and propagation studies as well as input to solar modulation models. A method for such an analysis and illustrative results are presented.

4 pages, 8 figures, in the 2013 ICRC conference, Rio de Janiero, Brazil, 2-9 July 2013

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• Interpretation of AMS-02 electrons and positrons data
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• Cosmic ray spectrum in the local Galaxy
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• Multi-wavelength Emission from the Fermi Bubble III. Stochastic (Fermi) Re-Acceleration of Relativistic Electrons Emitted by SNRs
• Spectrum of Relativistic and Subrelativistic Cosmic Rays in the 100 pc Central Region
• Recent results in cosmic ray physics and their interpretation
• Recent extensions to GALPROP
• A tale of cosmic rays narrated in gamma rays by Fermi
• Production cross sections of gamma-rays, electrons, and positrons in p-p collisions