X-ray Polarimetry - a Tool for the Galactic center diagnosis

TL;DR

X-ray polarimetry offers a novel method to map the three-dimensional structure and history of the Galactic center, revealing the nature of its emission sources and past activity through polarization measurements.

Contribution

This paper introduces the application of X-ray polarimetry as a new observational tool to study the Galactic center's structure and history, enhancing understanding beyond traditional spectroscopy.

Findings

X-ray polarimetry can determine the 3D position of scattering material.

Polarization measurements can identify the primary emission source.

The technique can trace the supermassive black hole's activity history.

Abstract

Was the Milky Way galaxy a low-luminosity active galactic nucleus (AGN) in the past? Can we find traces of remnant structures supporting this idea? What is the three-dimensional arrangement of matter around our central supermassive black hole? A number of fundamental questions concerning our own Galactic center remain controversial. To reveal the structure of the high-energy sky around our galactic core, a technique more sensitive to the morphology of the emitters than spectroscopy is needed. In this lecture note, I describe how X-ray polarimetry can open a new observational window by precisely measuring the three-dimensional position of the scattering material in the Galactic center. The observed polarization degree and polarization position angle would also determine unambiguously the primary source of emission and trace the centennial history of our supermassive black hole by detecting echoes of its past activity thanks to astrophysical mirrors. Finally, the synergy between X-ray polarimetry and infrared and radio observations can be used to better constrain the geometry in the first hundred parsecs around the Galactic center.