Linearly and Circularly Polarized Emission in Sagittarius A*

TL;DR

This study uses relativistic ray-tracing to model polarized synchrotron radiation in Sagittarius A*, constraining accretion parameters and predicting polarimetric images for future observations.

Contribution

It presents a self-consistent treatment of birefringence effects in polarized emission modeling, linking MRI-driven accretion physics with observable polarization signatures.

Findings

Constrained MRI and electron heating parameters.

Predicted unique polarimetric images for Sgr A*.

Limited the orientation of the accretion torus.

Abstract

We perform general relativistic ray-tracing calculations of the transfer of polarized synchrotron radiation through the relativistic accretion flow in Sagittarius (Sgr) A*. Based on a two-temperature magneto-rotational-instability (MRI) induced accretion mode, the birefringence effects are treated self-consistently. By fitting the spectrum and polarization of Sgr A* from millimeter to near-infrared bands, we are able to not only constrain the basic parameters related to the MRI and the electron heating rate, but also limit the orientation of the accretion torus. These constraints lead to unique polarimetric images, which may be compared with future millimeter and sub-millimeter VLBI observations. In combination with general relativistic MHD simulations, the model has the potential to test the MRI with observations of Sgr A*.