Cosmic-ray-induced ionization in molecular clouds adjacent to supernova remnants

Abstract

Energetic gamma rays (GeV to TeV photon energy) have been detected toward several supernova remnants (SNR) that are associated with molecular clouds. If the gamma rays are produced mainly by hadronic processes rather than leptonic processes like bremsstrahlung, then the flux of energetic cosmic ray nuclei (>1 GeV) required to produce the gamma rays can be inferred at the site where the particles are accelerated in SNR shocks. It is of great interest to understand the acceleration of the cosmic rays of lower energy (<1 GeV) that accompany the energetic component. These particles of lower energy are most effective in ionizing interstellar gas, which leaves an observable imprint on the interstellar ion chemistry. A correlation of energetic gamma radiation with enhanced interstellar ionization can thus be used to support the hadronic origin of the gamma rays and to constrain the acceleration of ionizing cosmic rays in SNR. Using observational gamma ray data, the primary cosmic ray proton spectrum can be modeled for E >1 GeV, and careful extrapolation of the spectrum to lower energies offers a method to calculate the ionization rate of the molecular cloud.

Sant Cugat Forum on Astrophysics 2012, to apper in Cosmic-ray induced phenomenology in star-forming environments: Proceedings of the 2nd Session of the Sant Cugat Forum of Astrophysics (April 16-19, 2012), Olaf Reimer and Diego F. Torres (eds.), 8 pages, 3 figures

References in corpus (4)

• Fermi Large Area Telescope Observations of the Supernova Remnant G8.7-0.1
• Tracing the sources of cosmic rays with molecular ions
• Parameterization of the Angular Distribution of Gamma Rays Produced by p-p Interaction in Astronomical Environment
• Cosmic-ray-induced ionization in molecular clouds adjacent to supernova remnants - Tracing the hadronic origin of GeV gamma radiation