Prospects of using closure traces directly for imaging in Very Long Baseline Interferometry

Abstract

The reconstruction of the polarization of a source in radio interferometry is a challenging calibration problem since the reconstruction strongly depends on the gains and leakages that need to be inferred along with the image. This is particularly true for the Event Horizon Telescope (EHT) due to its small number of antennas, small signal-to-noise ratio and large gain corruptions. To recover linear polarization, one either has to infer the leakages and gains together with the image structure, or rely completely on calibration independent closure quantities. While the first approach has been explored in Very Long Baseline Interferometry (VLBI) for a long time, the later one has been less studied for polarimetry. Closure traces are a recently proposed concept of closure quantities that, in contrast to closure phases and closure amplitudes, are independent against both gains and leakages and carry the relevant information about the polarization of the source. Here we explore, how closure traces could be directly fitted to create an image and point out an imaging pipeline that succeeds in the direct imaging from closure traces. Since closure traces have a number of inherent degeneracies, multiple local image modes that can fit the data are detected. Therefore, a multiobjective imaging technique is needed to correctly sample this multimodality. Closure traces are not constraining enough for the EHT configuration in 2017 to recover an image directly, mainly due to the small number of antennas. For planned successors of the EHT however (with a significantly larger number of antennas), this option becomes feasible and performs competitive to the imaging with residual leakages.

Accepted for publication by A&A

References in corpus (33)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• Multi-Scale CLEAN deconvolution of radio synthesis images
• First Sagittarius A* Event Horizon Telescope Results. III: Imaging of the Galactic Center Supermassive Black Hole
• An optimized algorithm for multi-scale wideband deconvolution of radio astronomical images
• Imaging the Schwarzschild-radius-scale Structure of M87 with the Event Horizon Telescope using Sparse Modeling
• A ring-like accretion structure in M87 connecting its black hole and jet
• Super-resolution Full Polarimetric Imaging for Radio Interferometry with Sparse Modeling
• Evaluation of New Submillimeter VLBI Sites for the Event Horizon Telescope
• First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization
• Dynamical Imaging with Interferometry
• Hybrid Very Long Baseline Interferometry Imaging and Modeling with Themis
• Filamentary structures as the origin of blazar jet radio variability
• Wavelet-based decomposition and analysis of structural patterns in astronomical images
• Unified Radio Interferometric Calibration and Imaging with Joint Uncertainty Quantification
• Multi-frequency Black Hole Imaging for the Next-Generation Event Horizon Telescope
• Exploring the disk-jet connection in NGC 315
• Polarization calibration techniques for new-generation VLBI
• A D-term Modeling Code (DMC) for simultaneous calibration and full-Stokes imaging of very long baseline interferometric data
• An Updated Formalism For Line-Driven Radiative Acceleration and Implications for Stellar Mass Loss
• 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
• Invariants in Co-polar Interferometry: an Abelian Gauge Theory
• Dynamic and polarimetric VLBI imaging with a multiscalar approach
• Bayesian self-calibration and imaging in Very Long Baseline Interferometry
• Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron IV. The quasar 3C 345 at 18 cm: Magnetic field structure and brightness temperature
• Invariants in Polarimetric Interferometry: a non-Abelian Gauge Theory
• Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes
• CLEAN imaging systematics of M87 radio jet
• A Geometric View of Closure Phases in Interferometry
• Swarm intelligence for full Stokes dynamic imaging reconstruction of interferometric data
• Robust analysis of differential Faraday Rotation based on interferometric closure observables

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