Space Science Reviews

, Volume 36, Issue 1, pp 41-49

First online:

The relevance of molecular observations to gamma-ray astronomy

  • T. W. HartquistAffiliated withDepartment of Physics and Astronomy, University College London

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The interaction of cosmic rays with interstellar clouds may produce some of the observed gamma-ray sources. The use of molecular observations to estimate the cloud masses, which are used to derive cosmic-ray fluxes, is reviewed. Molecular diagnostics of high cosmic-ray ionization rates are discussed, and a detailed application of those diagnostics is summarised and presented as evidence that second-order Fermi acceleration is important in old supernova remnants and can produce cosmic rays of too low energy to induce gamma-ray emission.