Polarized Emission of Sagittarius A*

TL;DR

This study models the polarized millimeter and sub-millimeter emission from Sagittarius A* using a relativistic accretion flow model, highlighting its ability to match observed emission features and identifying areas needing further refinement.

Contribution

It introduces a comprehensive relativistic model for polarized emission from Sagittarius A* that accounts for various radiative processes and explores parameter degeneracies.

Findings

Model reproduces millimeter to sub-millimeter emission with specific parameters.

Predicted near-infrared and X-ray fluxes are lower than observed quiescent levels.

Degeneracy exists between electron heating and magnetic parameters.

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 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 sub-millimeter emission characteristics with an accretion rate of ~6x10^17g.s^-1 and an inclination angle of ~40 deg. However, the corresponding model predicted near-infrared 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 general relativistic treatment with the black hole spin incorporated will resolve these issues.