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The Interaction of Cosmic Rays with Molecular Clouds in the Galactic Center
Thursday, May 17, 2018 - 3:30pm PDT
The ISM in the inner few hundred pc of the Galactic center differs from elsewhere in the Galaxy. This region is centered on a 4 million supermassive black hole and is occupied by a large concentration of molecular gas with high column density, high velocity dispersion and high gas temperature. Recent IR and X-ray observations indicate that the cosmic ray ionization rate is higher than elsewhere in the Galaxy by one to two orders of magnitudes.
The interaction of an enhanced cosmic-ray flux with molecular clouds in this region explains a number of observations: i) the ubiquitous warm molecular gas observed throughout the Galactic center, ii) the power law spectrum of GeV emission, iii) FeI Kalpha emission at 6.4 keV and iv) the unusual chemistry of molecular gas, as probed by a number of molecular tracers. In this picture, relativistic bremsstrahlung radiation explains the origin of diffuse gamma-ray and 6.4 keV line emission from the Galactic center region.