The Cosmic Ray Population of the Galactic Central Molecular Zone

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 gamma-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 gamma-ray emission. The model only partially explains the observed gamma-ray and radio emission. The model for the gamma-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 gamma-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.

9 pages, 5 figures, accepted for publication in the Astrophysical Journal

References in corpus (4)

• Spatial distribution of interstellar gas in the innermost 3 kpc of our Galaxy
• The Starburst Contribution to the Extra-Galactic Gamma-Ray Background
• Winds, Clumps, and Interacting Cosmic Rays in M82
• GBT Multiwavelength Survey of the Galactic Center Region

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• Cosmic-Ray Models of the Ridge-Like Excess of Gamma Rays in the Galactic Center
• Breaking the Radio - Gamma-Ray Connection in Arp 220
• Neutrino lighthouse powered by Sagittarius A* disk dynamo
• Does the SN rate explain the very high energy cosmic rays in the central 200 pc of our Galaxy?
• Synchrotron and Compton Spectra from a Steady-State Electron Distribution
• Galaxies at a Cosmic-Ray Eddington Limit
• Dark matter properties implied by gamma ray interstellar emission models
• High Energy Emission from the Galactic Center