Dynamic and polarimetric VLBI imaging with a multiscalar approach

Abstract

Recently multiscale imaging approaches such as DoG-HiT were developed to solve the VLBI imaging problem and showed a promising performance: they are fast, accurate, unbiased and automatic. We extend the multiscalar imaging approach to polarimetric imaging, reconstructions of dynamically evolving sources and finally to dynamic polarimetric reconstructions. These extensions (mr-support imaging) utilize a multiscalar approach. The time-averaged Stokes I image is decomposed by a wavelet transform into single subbands. We use the set of statistically significant wavelet coefficients, the multiresolution support, computed by DoG-HiT as a prior in a constrained minimization manner: we fit the single-frame (polarimetric) observables by only varying the coefficients in the multiresolution support. The EHT is a VLBI array imaging supermassive black holes. We demonstrate on synthetic data that mr-support imaging offers ample regularization and is able to recover simple geometric dynamics at the horizon scale in a typical EHT setup. The approach is relatively lightweight, fast and largely automatic and data driven. The ngEHT is a planned extension of the EHT designed to recover movies at the event horizon scales of a supermassive black hole. We benchmark the performance of mr-support imaging for the denser ngEHT configuration demonstrating the major improvements the additional ngEHT antennas will bring to dynamic, polarimetric reconstructions. Current and upcoming instruments offer the observational possibility to do polarimetric imaging of dynamically evolving structural patterns with highest spatial and temporal resolution. State-of-the-art dynamic reconstruction methods can capture this motion with a range of temporal regularizers and priors. With this work, we add an additional, simpler regularizer to the list: constraining the reconstruction to the multiresolution support.

accepted for publication in A&A

References in corpus (23)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• 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
• Compressed sensing imaging techniques for radio interferometry
• MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VIII. Faraday rotation in parsec-scale AGN jets
• Imaging the Schwarzschild-radius-scale Structure of M87 with the Event Horizon Telescope using Sparse Modeling
• Key Science Goals for the Next-Generation Event Horizon Telescope
• Radio and Millimeter Monitoring of Sgr A*: Spectrum, Variability, and Constraints on the G2 Encounter
• Millimeter light curves of Sagittarius A* observed during the 2017 Event Horizon Telescope campaign
• LOFAR Sparse Image Reconstruction
• Super-resolution Full Polarimetric Imaging for Radio Interferometry with Sparse Modeling
• Evaluation of New Submillimeter VLBI Sites for the Event Horizon Telescope
• Dynamical Imaging with Interferometry
• Hybrid Very Long Baseline Interferometry Imaging and Modeling with Themis
• Wavelet-based decomposition and analysis of structural patterns in astronomical images
• Unified Radio Interferometric Calibration and Imaging with Joint Uncertainty Quantification
• GRMHD/RMHD Simulations and Stability of Magnetized Spine-Sheath Relativistic Jets
• Selective Dynamical Imaging of Interferometric Data
• An Updated Formalism For Line-Driven Radiative Acceleration and Implications for Stellar Mass Loss
• Multi-scale and Multi-directional VLBI Imaging with CLEAN
• 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

Cited by in corpus (1)

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