Tsukuba Uchu Forum

120th Uchu Forum

Structure of the magnetic field driving active galactic nuclear jets probed by polarized light images

Yu Tsuneto

Kyoto University


With the success of the Event Horizon Telescope in directly imaging a supermassive black hole, the study of black holes has entered a new era in which the properties of black holes are explored through imaging observations. In particular, the polarized images reveal the magnetic field structure near the black hole, which gives clues to the formation and driving mechanism of active galactic nuclear jets. In this study, we theoretically predict the polarization image of the polarization components, the Stokes parameters (I, Q, U, V), by performing general relativistic radiation transport calculations taking into account synchrotron radiation, self-absorption, and the Faraday effect.

First, for M87*, linearly polarized vectors undergoe strong Faraday rotation due to the disk component, and the intensity of the polarization is reduced in observations. We also present a scenario in which the circularly polarized light component, which has been considered faint, is amplified due to Faraday rotation from the linearly polarized light in the high-temperature, high-density region near the black hole, and its image features reflect the aligned magnetic field structure for the first time.

Secondly, for Sgr A* at the Galactic center, we confirmed that the extended emission from the disk produces a ring-like image when the observer views it from above, and a trident-like image when viewed from the side. As for the polarization component, we present scenarios in which a circularly polarized image with a "borderline" structure reflecting the helical magnetic field in the disk and a linearly polarized image with a correspondingly high intensity are obtained.

In this talk I will discuss the relationship between the deviations between the intensity, linear and circular polarization distributions in an image and the magnetic field plasmas structure in a unified manner that considers multi-wavelength observations of the large-scale structure of the jet.