Nonthermal THz to TeV Emission from Stellar Wind Shocks in the Galactic Center

Abstract

The central parsec of the Galaxy contains dozens of massive stars with a cumulative mass-loss rate of similar to 10(-3) M-circle dot yr(-1). Shocks among these stellar winds produce the hot plasma that pervades the central part of the Galaxy. We argue that these stellar wind shocks also efficiently accelerate electrons and protons to relativistic energies. The relativistic electrons inverse Compton scatter the ambient ultraviolet and far-infrared radiation field, producing high-energy gamma-rays with a roughly constant luminosity from similar to GeV to similar to 10 TeV. This can account for the TeV source seen by HESS in the Galactic center. Our model predicts a GLAST counterpart to the HESS source with a luminosity of approximate to 10(35) ergs s(-1) and cooling break at approximate to 4 GeV. Synchrotron radiation from the same relativistic electrons should produce detectable emission at lower energies, with a surface brightness of approximate to 10-B-14(-3)2 ergs s(-1) cm(-2) arcsec(-2) from similar to THz to similar to keV, where B-3 is the magnetic field strength in units of mG. The observed level of diffuse thermal X-ray emission in the central parsec requires mG in our models. Future detection of B <= 300 the diffuse synchrotron background in the central parsec can directly constrain the magnetic field strength, providing an important boundary condition for models of accretion onto Sgr A*.