Polarized emission of sagittarius a

Abstract

We explore the parameter space of the two-temperature pseudo-Newtonian Keplerian accretion flow model for the millimeter and shorter wavelength emission from Sagittarius A*. A general relativistic (GR) ray-tracing code is used to treat the radiative transfer of polarized synchrotron emission from the flow. The synchrotron self-Comptonization and bremsstrahlung emission components are also included. It is shown that the model can readily account for the millimeter to submillimeter emission characteristics with an accretion rate of 6 × 1017 g s-1 and an inclination angle of ̃ 40°. However, the corresponding model-predicted near-infrared (NIR) and X-ray fluxes are more than one order of magnitude lower than the observed "quiescent" state values. While the extended quiescent-state X-ray emission has been attributed to thermal emission from the large-scale accretion flow, the NIR emission and flares are likely dominated by emission regions either within the last stable orbit of a Schwarzschild black hole or associated with outflows. With the viscous parameter derived from numerical simulations, there is still a degeneracy between the electron heating rate and the magnetic parameter. A fully GR treatment with the black hole spin incorporated will resolve these issues. © 2009 The American Astronomical Society. All rights reserved.