Polarization images of accretion flow around supermassive black holes: imprints of toroidal field structure

Abstract

With unprecedented angular resolution, the Event Horizon Telescope (EHT) has opened a new era of black holes. We have previously calculated the expected polarization images of M87* with the EHT observations in mind. There, we demonstrated that circular polarization (CP) images, as well as the linear polarization (LP) maps, can convey quite useful information to us, such as the flow structure and magnetic field configuration around the black hole. In this paper, we make new predictions for the cases in which disk emission dominates over jet emission, bearing Sgr A* in mind. Here we set the proton-to-electron temperature ratio of the disk component to be Tp/Te $\sim$ 2 so as to suppress jet emission relative to emission from accretion flow. As a result, we obtain ring-like images and triple-forked images around the black hole for face-on and edge-on cases, respectively. We also find significant CP components in the images ($\gtrsim 10\%$ in fraction), both with positive and negative signs, amplified through the Faraday conversion, not sensitively depending on the inclination angles. Furthermore, we find a "separatrix" in the CP images, across which the sign of CP is reversed and on which the LP flux is brightest, that can be attributed to the helical magnetic field structure in the disk. These results indicate that future full polarization EHT images are a quite useful tracer of the magnetic field structure. We also discuss to what extent we will be able to extract information regarding the magnetic field configurations, under the scattering in the interstellar plasma, in future EHT polarimetric observations of Sgr A*.

17 pages, 13 figures, and 1 table. Accepted for publication in PASJ

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Cited by in corpus (14)

• First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization
• Mildly Super-Eddington Accretion Onto Slowly-Spinning Black Holes Explains the X-Ray Weakness of the Little Red Dots
• Quantum effects on the black hole shadow and deflection angle in presence of plasma
• Black Hole Magnetic Fields and Their Imprint on Circular Polarization Images
• Polarimetric signatures of the photon ring of a black hole that is pierced by a cosmic axion string
• Component of energy flow from supercritical accretion disks around rotating stellar mass black holes
• How Spatially Resolved Polarimetry Informs Black Hole Accretion Flow Models
• Probing Axions via Light Circular Polarization and Event Horizon Telescope
• RAIKOU: A General Relativistic, Multi-wavelength Radiative Transfer Code
• Photon ring polarimetry with next-generation black hole imaging I. M87*
• Jet Archaeology and Forecasting: Image Variability and Magnetic Field Configuration
• Diverse Polarimetric Features of AGN Jets from Various Viewing Angles: Towards a Unified View
• Investigating the Disk-Jet Structure in M87 through Flux Separation in the Linear and Circular Polarization Images
• Radiative energy from a reconnection region around massive black hole