A Possible Link Between the Galactic Center HESS Source and Sgr A*

Abstract

Recently, HESS and other air Cerenkov telescopes have detected a source of TeV gamma-rays coincident with the Galactic center. It is not yet clear whether the gamma-rays are produced via leptonic or hadronic processes, so it is important to consider possible acceleration sites for the charged particles which produce the gamma-rays. One exciting possibility for the origin of these particles is the central black hole, Sgr A*, where the turbulent magnetic fields close to the event horizon can accelerate protons to TeV energies. Using a realistic model of the density distribution in a 6 pc x 6 pc x 6pc cube at the Galactic center, we here calculate the trajectories followed by these TeV protons as they gyrate through the turbulent medium surrounding Sgr A*. Diffusing out from the black hole, the protons produce TeV gamma-rays via pi^0 decay following a collision with a proton in the surrounding medium. After following over 222,000 such trajectories, we find that the circumnuclear ring around Sgr A* can reproduce the observed 0.1-100 TeV HESS spectrum and flux if the protons are injected into this medium with an effective power-law index of 0.75, significantly harder than the observed photon index of 2.25. The total energy in the steady-state 1-40 TeV proton population surrounding Sgr A* is inferred to be approx 5x10^{45} ergs. Only 31% of the emitted 1-100 TeV protons encounter the circumnuclear torus, leaving a large flux of protons that diffuse outward to contribute to the Galactic ridge emission observed by HESS on scales of >~ 1 degree.

4 pages, 2 figures, accepted to ApJ Letters

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Cited by in corpus (28)

• Spectrum and variability of the Galactic Center VHE gamma-ray source HESS J1745-290
• Galactic center at very high-energies
• Multi-wavelength signals of dark matter annihilations at the Galactic center
• Concurrent X-ray, near-infrared, sub-millimeter, and GeV gamma-ray observations of Sgr A*
• Diffuse Hard X-ray Emission in Starburst Galaxies as Synchrotron from Very High Energy Electrons
• TeV Gamma-ray Observations of The Galactic Center Ridge By VERITAS
• Non-thermal Processes in Black-Hole-Jet Magnetospheres
• Simultaneous H.E.S.S. and Chandra observations of Sagittarius A* during an X-ray flare
• Sagittarius A* as an Origin of the Galactic PeV Cosmic Rays?
• Ultra-High-Energy Cosmic Rays from the Radio Lobes of AGNs
• Diffuse TeV Emission at the Galactic Centre
• High Energy Cosmic-ray Diffusion in Molecular Clouds: A Numerical Approach
• Hadronic origin of multi-TeV gamma rays and neutrinos from low-luminosity active galactic nuclei: implications of past activities of the Galactic center
• A Leptonic Model of Steady High-Energy Gamma-Ray Emission from Sgr A${}^{\ast }$
• Leptonic origin of the 100 MeV gamma-ray emission from the Galactic Centre
• Hybrid model of GeV-TeV gamma ray emission from Galactic Center
• A Numerical Assessment of Cosmic-ray Energy Diffusion through Turbulent Media
• Diffusive Cosmic Ray Acceleration at the Galactic Centre
• Exploring the Nature of the Galactic Center Gamma-Ray Source with the Cherenkov Telescope Array
• Diffusive Cosmic-ray Acceleration in Sagittarius A*
• Diffusion of Cosmic Rays in a Multiphase Interstellar Medium Swept-Up by a Supernova Remnant Blast Wave
• Modelling the time dependence of the TeV Gamma-ray source at the Galactic Centre
• Assessing the Feasibility of Cosmic-Ray Acceleration by Magnetic Turbulence at the Galactic Center
• High-(Energy)-Lights -- The Very High Energy Gamma-Ray Sky
• Radio Synchrotron Emission from Secondary Leptons in the Vicinity of Sgr A*
• Magnetic neutral points and electric lines of force in strong gravity of a rotating black hole
• High Energy Emission from the Galactic Center
• Search for long-term variability of HESS J1745-290