The Galactic Center: A PeV Cosmic Ray Acceleration Factory

Abstract

The multi-TeV $\gamma$-rays from the Galactic Center (GC) have a cutoff at tens of TeV, whereas the diffuse emission has no such cutoff, which is regarded as an indication of PeV proton acceleration by the HESS experiment. It is important to understand the inconsistency and study the possibility that PeV cosmic-ray acceleration could account for the apparently contradictory point and diffuse $\gamma$-ray spectra. In this work, we propose that the cosmic rays are accelerated up to $>$PeV in GC. The interaction between cosmic rays and molecular clouds is responsible for the multi-TeV $\gamma$-ray emissions from both the point source and diffuse sources today. Enhanced by the small volume filling factor (VFF) of the clumpy structure, the absorption of the $\gamma$-rays leads to a sharp cutoff spectrum at tens of TeV produced in the GC. Away from galactic center, the VFF grows and the absorption enhancement becomes negligible. As a result, the spectra of $\gamma$-ray emissions for both point source and diffuse sources can be successfully reproduced under such self-consistent picture. In addition, a "surviving-tail" at $\sim$100 TeV is expected from the point source, which can be observed by future projects CTA and LHAASO. Neutrinos are simultaneously produced during proton-proton (PP) collision. With 5-10 years observations, the KM3Net experiment will be able to detect the PeV source according to our calculation.

References in corpus (8)

• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• Acceleration of petaelectronvolt protons in the Galactic Centre
• A large light-mass component of cosmic rays at 10^{17} - 10^{17.5} eV from radio observations
• Physics Reach of High-Energy and High-Statistics IceCube Atmospheric Neutrino Data
• Guaranteed and Prospective Galactic TeV Neutrino Sources
• Neutrino Lighthouse at Sagittarius A*
• A Systematic Chandra study of Sgr A${}^{\star }$: I. X-ray flare detection
• Hadronic origin of multi-TeV gamma rays and neutrinos from low-luminosity active galactic nuclei: implications of past activities of the Galactic center

Cited by in corpus (8)

• High-energy particles and radiation in star-forming regions
• Cosmic ray production in supernovae
• The Highest Energy HAWC Sources are Likely Leptonic and Powered by Pulsars
• Sagittarius A* as an Origin of the Galactic PeV Cosmic Rays?
• Galactic PeVatrons and helping to find them: Effects of Galactic absorption on the observed spectra of very high energy $\gamma$-ray sources
• New prototype scintillator detector for the Tibet AS$\gamma$ Experiment
• HESS J1745$-$290 spectrum explained by a transition in the diffusion regime of PeV cosmic rays in the Sgr A* accretion flow
• High Energy Emission from the Galactic Center