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Implications of High Cosmic Ray Flux in the Galactic Center

Published onJun 01, 2020
Implications of High Cosmic Ray Flux in the Galactic Center

There has recently been significant appreciation of the role of cosmic rays in the Galactic center region. This stems from recent radio continuum observations showing a 400 pc MeerKAT bubble surrounding the Galactic center. Although this bubble is one of the largest structures noted in the Galactic center, it is possible that this feature lies at the base of the Fermi bubbles. The evidence for the bubble suggests that cosmic ray-driven winds inflate this large-scale bubble. This interpretation supports a number of independent measurements indicating that cosmic ray flux is high in this region: 1) warm molecular clouds produced by cosmic ray heating, 2) a high cosmic ray ionization rate, 100-1000 times higher than in the Galaxy, is needed to explain H3+ observations and 3) the contribution of low-energy cosmic rays in producing the 6.4 keV line emission. Lastly, the origin of nonthermal radio filaments has been explained in the context of cosmic ray driven winds interacting with stellar wind bubbles. To test this model, we have recently identified a number of compact sources that appear to be associated with nonthermal filaments. An overview of these topics and the importance of cosmic rays within a few degrees of the Galactic center will be discussed.

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