Nonthermal Electrons in Radiatively Inefficient Accretion Flow Models of Sagittarius A*

We investigate radiatively inefficient accretion flow models for Sgr A*, the supermassive black hole in our Galactic Center, in light of new observational constraints. Confirmation of linear polarization in the submm emission argues for accretion rates much less than the canonical Bondi rate. We consider models with low accretion rates and calculate the spectra produced by a hybrid electron population, consisting of both thermal and nonthermal particles. The thermal electrons produce the submm emission and can account for its linear polarization properties. The observed low-frequency radio spectrum can be explained if a small fraction (≈ 1.5%) of the electron thermal energy resides in a soft power-law tail. In the innermost region of the accretion flow, turbulence and/or magnetic reconnection events may occasionally accelerate a fraction of the electrons into a harder power-law tail. We show that the synchrotron emission from these electrons, or the Compton up-scattering of synchrotron photons by these electrons, may account for the X-ray flares observed by Chandra. Subject headings: accretion, accretion disks – black hole physics – galaxies: active – Galaxy: center – radiation mechanisms: thermal – radiation mechanisms: nonthermal