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Abstract Measuring the 3D spatial distribution of magnetic fields in the interstellar medium and the intracluster medium is crucial yet challenging. The probing of the 3D magnetic field’s 3D distribution, including the field plane-of-sky orientation (ψ), the magnetic field’s inclination angle (γ) relative to the line of sight, and the magnetization (∼the inverse Alfvén Mach number ), at different distances from the observer makes the task even more formidable. However, the anisotropy and Faraday decorrelation effect in polarized synchrotron emission offer a unique solution. We show that due to the Faraday decorrelation, only regions up to a certain effective path length along the line of sight contribute to the statistical correlation of the measured polarization. The 3D spatial information can be consequently derived from synchrotron polarization derivatives (SPDs), which are calculated from the difference in synchrotron polarization across two wavelengths. We find that the 3D magnetic field can be estimated from the anisotropy observed in SPDs: the elongation direction of the SPD structures probesψ, and the degree of SPD anisotropy, along with its morphological curvature, provides insights into andγ. To extract these anisotropic features and their correlation with the 3D magnetic field, we propose utilizing a machine learning approach, specifically the Vision Transformer (ViT) architecture, which was exemplified by the success of ChatGPT. We train the ViT using synthetic synchrotron observations generated from magnetohydrodynamic turbulence simulations in sub-Alfvénic and super-Alfvénic conditions. We show that ViT’s application to multiwavelength SPDs can successfully reconstruct the 3D magnetic fields’ 3D spatial distribution.
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Investigating the Disk–Jet Structure in M87 through Flux Separation in the Linear and Circular Polarization Images
Abstract For testing different electron temperature (Te) prescriptions in general relativistic magnetohydrodynamics (GRMHD) simulations through observations, we propose to utilize linear polarization (LP) and circular polarization (CP) images. We calculate the polarization images based on a semi-magnetically arrested disk GRMHD model for variousTeparameters, bearing M87 in mind. We find an LP–CP separation in the images of the low-Tedisk cases at 230GHz; namely, the LP flux mainly originates from downstream of the jet, and the CP flux comes from the counter-side jet, while the total intensity is maximum at the jet base. This can be understood as follows: although the LP flux is generated through synchrotron emission widely around the black hole, most of the LP flux from the jet base does not reach the observer, since it undergoes Faraday rotation ( ) when passing through the outer cold disk and is thus depolarized. Hence, only the LP flux from the downstream (not passing the cold dense plasmas) can survive. Meanwhile, the CP flux is generated from the LP flux by Faraday conversion ( ∝Te) in the inner hot region. Stronger CP flux is thus observed from the counter-side jet. Moreover, the LP–CP separation is more enhanced at a lower frequency, such as 86 GHz, but is rather weak at 43 GHz, since the media in the latter case is optically thick for synchrotron self-absorption so that all of the fluxes should come from the photosphere. The same is true for cases with higher mass accretion rates and/or larger inclination angles.
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- Award ID(s):
- 2034306
- PAR ID:
- 10367378
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 931
- Issue:
- 1
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 25
- Size(s):
- Article No. 25
- Sponsoring Org:
- National Science Foundation
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