Hybrid Very Long Baseline Interferometry Imaging and Modeling with Themis

Abstract

Generating images from very long baseline interferometric observations poses a difficult, and generally not unique, inversion problem. This problem is simplified by the introduction of constraints, some generic (e.g., positivity of the intensity) and others motivated by physical considerations (e.g., smoothness, instrument resolution). It is further complicated by the need to simultaneously address instrumental systematic uncertainties and sparse coverage in the u-v plane. We report a new Bayesian image reconstruction technique in the parameter estimation framework Themis that has been developed for the Event Horizon Telescope. This has two key features: first, the full Bayesian treatment of the image reconstruction makes it possible to generate a full posterior for the images, permitting a rigorous and quantitative investigation into the statistical significance of image features. Second, it is possible to seamlessly incorporate directly modeled features simultaneously with image reconstruction. We demonstrate this second capability by incorporating a narrow, slashed ring in reconstructions of simulated M87 data in an attempt to detect and characterize the photon ring. We show that it is possible to obtain high-fidelity photon ring sizes, enabling mass measurements with accuracies of 2%-5% that are essentially insensitive to astrophysical uncertainties, and creating opportunities for precision tests of general relativity.

References in corpus (10)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• First M87 Event Horizon Telescope Results. II. Array and Instrumentation
• First M87 Event Horizon Telescope Results. III. Data Processing and Calibration
• 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
• Unified Radio Interferometric Calibration and Imaging with Joint Uncertainty Quantification
• Bayesian Inference for Radio Observations

Cited by in corpus (14)

• First Sagittarius A* Event Horizon Telescope Results. III: Imaging of the Galactic Center Supermassive Black Hole
• First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass
• Observing the Inner Shadow of a Black Hole: A Direct View of the Event Horizon
• Key Science Goals for the Next-Generation Event Horizon Telescope
• First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization
• The Photon Ring in M87*
• Resolving the inner parsec of the blazar J1924-2914 with the Event Horizon Telescope
• How narrow is the M87* ring? II. A new geometric model
• The Event Horizon Telescope Image of the Quasar NRAO 530
• A D-term Modeling Code (DMC) for simultaneous calibration and full-Stokes imaging of very long baseline interferometric data
• Multi-scale and Multi-directional VLBI Imaging with CLEAN
• Dynamic and polarimetric VLBI imaging with a multiscalar approach
• Time-dependent visibility modelling of a relativistic jet in the X-ray binary MAXI J1803-298
• Relativistic Signatures of Flux Eruption Events Near Black Holes