The Cosmic-Ray Population of the Galactic Central Molecular Zone

Type Journal Article
Names Tova M. Yoast-Hull, J. S., III Gallagher, Ellen G. Zweibel
Publication The Astrophysical Journal
Volume 790
Pages 86
Journal Abbreviation The Astrophysical Journal
Date August 1, 2014
DOI 10.1088/0004-637X/790/2/86
ISSN 0004-637X
URL http://adsabs.harvard.edu/abs/2014ApJ...790...86Y
Library Catalog adslabs.org
Abstract The conditions in the Galactic Center are often compared with those in starburst systems, which contain higher supernova rates, stronger magnetic fields, more intense radiation fields, and larger amounts of dense molecular gas than in our own Galactic disk. Interactions between such an augmented interstellar medium and cosmic rays result in brighter radio and γ-ray emission. Here, we test how well the comparisons between the Galactic Center and starburst galaxies hold by applying a model for cosmic-ray interactions to the Galactic Center to predict the resulting γ-ray emission. The model only partially explains the observed γ-ray and radio emission. The model for the γ-ray spectrum agrees with the data at TeV energies but not at GeV energies. Additionally, as the fits of the model to the radio and γ-ray spectra require significant differences in the optimal wind speed and magnetic field strength, we find that the single-zone model alone cannot account for the observed emission from the Galactic Center. Our model is improved by including a soft, additional cosmic-ray population. We assess such a cosmic-ray population and its potential sources and find that a cosmic-ray electron spectrum is energetically favored over a cosmic-ray proton spectrum.
Tags COSMIC RAYS, Galaxy: Center, galaxies: starburst, gamma rays: galaxies, radio continuum: galaxies
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