Multiobjective optimization for scattering mitigation and scattering screen reconstruction in VLBI observations of the Galactic Center

Abstract

Imaging reconstruction of interferometric data is a hard ill-posed inverse problem. Its difficulty is increased when observing the Galactic Center, which is obscured by a scattering screen. This is because the scattering breaks the one-to-one correspondence between images and visibilities. Solving the scattering problem is one of the biggest challenges in radio imaging of the Galactic Center. In this work we present a novel strategy to mitigate its effect and constrain the screen itself using multiobjective optimization. We exploit the potential of evolutionary algorithms to describe the optimization landscape to recover the intrinsic source structure and the scattering screen affecting the data. We successfully recover both the screen and the source in a wide range of simulated cases, including the speed of a moving screen at 230 GHz. Particularly, we can recover a ring structure in scattered data at 86 GHz. Our analysis demonstrates the huge potential that recent advancements in imaging and optimization algorithms offer to recover image structures, even in weakly constrained and degenerated, possibly multi-modal settings. The successful reconstruction of the scattering screen opens the window to event horizon scale works on the Galactic Center at 86G Hz up to 116 GHz, and the study of the scattering screen itself.

To appear in A&A

References in corpus (49)

• 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. 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
• Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center 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
• First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multi-wavelength Observations, Data Processing, and Calibration
• First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass
• General relativistic magnetohydrodynamical simulations of the jet in M87
• High Resolution Linear Polarimetric Imaging for the Event Horizon Telescope
• Interferometric Imaging Directly with Closure Phases and Closure Amplitudes
• Detection of the Intrinsic Size of Sagittarius A* through Closure Amplitude Imaging (includes Online Supporting Material)
• Imaging the Schwarzschild-radius-scale Structure of M87 with the Event Horizon Telescope using Sparse Modeling
• Discovery of a radio emitting neutron star with an ultra-long spin period of 76 seconds
• BlackHoleCam: fundamental physics of the Galactic center
• A ring-like accretion structure in M87 connecting its black hole and jet
• Observational appearance of inefficient accretion flows and jets in 3D GRMHD simulations: Application to Sgr~A*
• Radio and Millimeter Monitoring of Sgr A*: Spectrum, Variability, and Constraints on the G2 Encounter
• The Size, Shape, and Scattering of Sagittarius A* at 86 GHz: First VLBI with ALMA
• Millimeter light curves of Sagittarius A* observed during the 2017 Event Horizon Telescope campaign
• Super-resolution Full Polarimetric Imaging for Radio Interferometry with Sparse Modeling
• The Scattering and Intrinsic Structure of Sagittarius A* at Radio Wavelengths
• Evaluation of New Submillimeter VLBI Sites for the Event Horizon Telescope
• The Angular Broadening of the Galactic Center Pulsar SGR J1745-29: A New Constraint on the Scattering Medium
• First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization
• Theory and Simulations of Refractive Substructure in Resolved Scatter-Broadened Images
• Imaging an Event Horizon: Mitigation of Scattering Toward Sagittarius A*
• Dynamical Imaging with Interferometry
• Evidence for an abundant old population of Galactic ultra long period magnetars and implications for fast radio bursts
• Stochastic Optics: A Scattering Mitigation Framework for Radio Interferometric Imaging
• Locating the intense interstellar scattering towards the inner Galaxy
• The Optics of Refractive Substructure
• Selective Dynamical Imaging of Interferometric Data
• First Very Long Baseline Interferometry Detections at 870μm
• An Updated Formalism For Line-Driven Radiative Acceleration and Implications for Stellar Mass Loss
• 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
• Imaging a ring-like structure and the extended jet of M87 at 86 GHz
• Swarm intelligence for full Stokes dynamic imaging reconstruction of interferometric data
• Observational constraints in Delta Gravity: CMB and supernovas
• Prospects of using closure traces directly for imaging in Very Long Baseline Interferometry