Synchrotron Radiation from Radiatively Inefficient Accretion Flow Simulations: Applications to Sagittarius A*

Abstract

We calculate synchrotron radiation in three-dimensional pseudo-Newtonian magnetohydrodynamic simulations of radiatively inefficient accretion flows. We show that the emission is highly variable at optically thin frequencies, with order-of-magnitude variability on timescales as short as the orbital period near the last stable orbit; this emission is linearly polarized at the ~20%-50% level because of the coherent toroidal magnetic field in the flow. At optically thick frequencies, both the variability amplitude and polarization fraction decrease significantly with decreasing photon frequency. We argue that these results are broadly consistent with the observed properties of Sgr A* at the Galactic center, including the rapid infrared flaring.