A Possible Link between the Galactic Center HESS Source and Sagittarius A*

Recently, HESS and other air Cerenkov telescopes have detected a source ofTeV gamma-rays coincident with the Galactic center. It is not yet clear whetherthe gamma-rays are produced via leptonic or hadronic processes, so it isimportant to consider possible acceleration sites for the charged particleswhich produce the gamma-rays. One exciting possibility for the origin of theseparticles is the central black hole, Sgr A*, where the turbulent magneticfields close to the event horizon can accelerate protons to TeV energies. Usinga realistic model of the density distribution in a 6 pc x 6 pc x 6pc cube atthe Galactic center, we here calculate the trajectories followed by these TeVprotons as they gyrate through the turbulent medium surrounding Sgr A*.Diffusing out from the black hole, the protons produce TeV gamma-rays via pi^0decay following a collision with a proton in the surrounding medium. Afterfollowing over 222,000 such trajectories, we find that the circumnuclear ringaround Sgr A* can reproduce the observed 0.1-100 TeV HESS spectrum and flux ifthe protons are injected into this medium with an effective power-law index of0.75, significantly harder than the observed photon index of 2.25. The totalenergy in the steady-state 1-40 TeV proton population surrounding Sgr A* isinferred to be approx 5x10^{45} ergs. Only 31% of the emitted 1-100 TeV protonsencounter the circumnuclear torus, leaving a large flux of protons that diffuseoutward to contribute to the Galactic ridge emission observed by HESS on scalesof >~ 1 degree.Comment: 4 pages, 2 figures, accepted to ApJ Letter