Probing circular polarization and magnetic field structure in AGN

Abstract

The magnetic field morphology of relativistic jets can be studied with circular polarization (CP). Recent 3D relativistic magnetohydrodynamic (RMHD) simulations coupled with radiative transfer calculations make strong predictions about the level (and morphology) of the jet's CP emission. These simulations show that the sign of CP and the electric vector position angle (EVPA) are both sensitive to the jet's magnetic field morphology within the radio core. We probe this theory by exploring if the jet's radio core EVPA orientation is consistent with the observed sign of the core CP in deep full-track polarimetric observations. We aim to probe the nature of linear polarization and CP in the innermost regions of jets from a small sample of nine blazars. This sample includes sources that have exhibited: (i) positive CP, (ii) negative CP, or (iii) positive & negative CP simultaneously in the radio core region. Nine blazar sources were observed using the VLBA at both 15 GHz and 23 GHz. Our self-calibration relies on a physically based model applied in DoG-HiT resulting in more accurate gains. We consider compact Stokes V structures instead of assuming it to be zero, which is crucial given the significant non-zero CP fraction observed at long baselines. We observe robust, relatively high degrees of fractional circular polarization m_c=(0.32 +- 0.2)% at 15 GHz and m_c=(0.59 +-0.56)% at 23 GHz. We observe consistent polarized structure and EVPA orientation over time when comparing our analysis with archival MOJAVE data. Theoretical predictions indicate a clear favored toroidal magnetic field orientation within the extended jet emission of the reconstructed signal of the blazar 0149+218. The jet structures of 1127-145 and 0528+134, even in superresolution, exhibit characteristics aligned with helical or poloidal magnetic nature.

References in corpus (39)

• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• First M87 Event Horizon Telescope Results. VII. Polarization of the Ring
• Kinematics of Parsec-Scale Jets of Gamma-Ray Blazars at 43~GHz within the VLBA-BU-BLAZAR Program
• Revisiting the radio interferometer measurement equation. I. A full-sky Jones formalism
• MOJAVE. XVII. Jet Kinematics and Parent Population Properties of Relativistically Beamed Radio-Loud Blazars
• High Resolution Linear Polarimetric Imaging for the Event Horizon Telescope
• Interferometric Imaging Directly with Closure Phases and Closure Amplitudes
• Magnetic field strength and spectral distribution of six parsec-scale active galactic nuclei jets
• Imaging the Schwarzschild-radius-scale Structure of M87 with the Event Horizon Telescope using Sparse Modeling
• Super-resolution Full Polarimetric Imaging for Radio Interferometry with Sparse Modeling
• Detection and Measurement of Parsec-Scale Circular Polarization in Four AGN
• MOJAVE: Monitoring of Jets in AGN with VLBA Experiments - II. First-Epoch 15 GHz Circular Polarization Results
• Variable structures in M87* from space, time and frequency resolved interferometry
• Parsec-Scale Circular Polarization Observations of 40 Blazars
• POLAMI: Polarimetric Monitoring of Active Galactic Nuclei at Millimetre Wavelengths. I. The program, calibration, and calibrators data products
• Full Polarization Spectra of 3C 279
• Comparison of classical and Bayesian imaging in radio interferometry
• Resolving the inner parsec of the blazar J1924-2914 with the Event Horizon Telescope
• Theoretical Models for Producing Circularly Polarized Radiation in Extragalactic Radio Sources
• High Levels of Circularly Polarized Emission from the Radio Jet in NGC 1275 (3C 84)
• F-GAMMA: Multi-frequency radio monitoring of Fermi blazars. The 2.64 to 43 GHz Effelsberg light curves from 2007-2015
• MOJAVE XVI: Multi-Epoch Linear Polarization Properties of Parsec-Scale AGN Jet Cores
• MOJAVE. XX. Persistent Linear Polarization Structure in Parsec-scale AGN Jets
• "Orphan" $\gamma$-ray Flares and Stationary Sheaths of Blazar Jets
• Multiwavelength Observations of the Gamma-Ray Blazar PKS 0528+134 in Quiescence
• The 15--43-GHz Parsec-scale Circular Polarization of 41 Active Galactic Nuclei
• Closure Traces: Novel Calibration-Insensitive Quantities for Radio Astronomy
• The Event Horizon Telescope Image of the Quasar NRAO 530
• Linear Polarization Properties of Parsec-Scale AGN~Jets
• GPCAL: a generalized calibration pipeline for instrumental polarization in VLBI data
• Using multiobjective optimization to reconstruct interferometric data (I)
• Multi-scale and Multi-directional VLBI Imaging with CLEAN
• Dynamic and polarimetric VLBI imaging with a multiscalar approach
• Bayesian self-calibration and imaging in Very Long Baseline Interferometry
• CLEAN imaging systematics of M87 radio jet
• MOJAVE XXI. Decade-long linear polarization variability in AGN jets at parsec scales
• Swarm intelligence for full Stokes dynamic imaging reconstruction of interferometric data
• Prospects of using closure traces directly for imaging in Very Long Baseline Interferometry
• Robust analysis of differential Faraday Rotation based on interferometric closure observables

Cited by in corpus (1)

• How to make CLEAN variants faster? Using clustered components informed by the autocorrelation function