A GeV-TeV particle component and the barrier of cosmic-ray sea in the Central Molecular Zone

TL;DR

This paper identifies GeV-TeV cosmic rays in the Galactic center's central molecular zone, revealing a high-energy accelerator and a barrier that limits cosmic-ray sea penetration, with implications for understanding cosmic-ray origins.

Contribution

It provides the first evidence of a high-energy particle accelerator at the Galactic center and suggests a barrier affecting cosmic-ray propagation into the central molecular zone.

Findings

Detection of GeV-TeV cosmic rays in the Galactic center

Lower cosmic-ray energy density than the cosmic-ray sea

Presence of a barrier restricting cosmic-ray penetration

Abstract

Cosmic rays are important probe of a number of fundamental physical problems such as the acceleration of high and very high energy particles in extreme astrophysical environments. The Galactic center is widely anticipated to be an important cosmic-ray source and the observations of some Imaging Atmospheric Cherenkov Telescopes did successfully reveal a component of TeV-PeV cosmic rays in the vicinity of the Galactic center. Here we report the identification of GeV-TeV cosmic rays in the central molecular zone with the $\gamma$-ray observations of the Fermi Large Area Telescope, whose spectrum and spatial gradient are consistent with that measured by the Imaging Atmospheric Cherenkov Telescopes but the corresponding cosmic-ray energy density is substantially lower than the so-called cosmic-ray sea component, suggesting the presence of a high energy particle accelerator at the Galactic center and the existence of a barrier that can effectively suppress the penetration of the particles from the cosmic-ray sea to the central molecular zone.