Dynamical Imaging with Interferometry

Abstract

By linking widely separated radio dishes, the technique of very long baseline interferometry (VLBI) can greatly enhance angular resolution in radio astronomy. However, at any given moment, a VLBI array only sparsely samples the information necessary to form an image. Conventional imaging techniques partially overcome this limitation by making the assumption that the observed cosmic source structure does not evolve over the duration of an observation, which enables VLBI networks to accumulate information as the Earth rotates and changes the projected array geometry. Although this assumption is appropriate for nearly all VLBI, it is almost certainly violated for submillimeter observations of the Galactic Center supermassive black hole, Sagittarius A* (Sgr A*), which has a gravitational timescale of only ~20 seconds and exhibits intra-hour variability. To address this challenge, we develop several techniques to reconstruct dynamical images ("movies") from interferometric data. Our techniques are applicable to both single-epoch and multi-epoch variability studies, and they are suitable for exploring many different physical processes including flaring regions, stable images with small time-dependent perturbations, steady accretion dynamics, or kinematics of relativistic jets. Moreover, dynamical imaging can be used to estimate time-averaged images from time-variable data, eliminating many spurious image artifacts that arise when using standard imaging methods. We demonstrate the effectiveness of our techniques using synthetic observations of simulated black hole systems and 7mm Very Long Baseline Array observations of M87, and we show that dynamical imaging is feasible for Event Horizon Telescope observations of Sgr A*.

16 Pages, 12 Figures, Accepted for publication in ApJ

References in corpus (51)

• Monitoring stellar orbits around the Massive Black Hole in the Galactic Center
• Measuring Distance and Properties of the Milky Way's Central Supermassive Black Hole with Stellar Orbits
• Viewing the Shadow of the Black Hole at the Galactic Center
• Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre
• Polarimetric Observations of 15 Active Galactic Nuclei at High Frequencies: Jet Kinematics from Bimonthly Monitoring with the Very Long Baseline Array
• MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VI. Kinematics Analysis of a Complete Sample of Blazar Jets
• Sub-milliarcsecond Imaging of Quasars and Active Galactic Nuclei III. Kinematics of Parsec-Scale Radio Jets
• Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum: II. Black-Hole Images
• Shapes and Positions of Black Hole Shadows in Accretion Disks and Spin Parameters of Black Holes
• A Parallax Distance to the Microquasar GRS 1915+105 and a Revised Estimate of its Black Hole Mass
• High Resolution Linear Polarimetric Imaging for the Event Horizon Telescope
• Imaging Optically-Thin Hot Spots Near the Black Hole Horizon of Sgr A* at Radio and Near-Infrared Wavelengths
• MOJAVE XIII. Parsec-Scale AGN Jet Kinematics Analysis Based on 19 years of VLBA Observations at 15 GHz
• The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations
• Resolved Magnetic-Field Structure and Variability Near the Event Horizon of Sagittarius A*
• An X-ray, IR, and Submillimeter Flare of Sagittarius A*
• 1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-Variable Emission on Event Horizon Scales
• Polarimetry of near-infrared flares from Sagittarius A*
• Imaging Bright Spots in the Accretion Flow Near the Black Hole Horizon of Sgr A*
• Imaging the Schwarzschild-radius-scale Structure of M87 with the Event Horizon Telescope using Sparse Modeling
• The Intrinsic Size of Sagittarius A* from 0.35 cm to 6 cm
• Methods for detecting flaring structures in Sagittarius A* with high frequency VLBI
• Sco X-1: The Evolution and Nature of the Twin Compact Radio Lobes
• Simultaneous Multi-Wavelength Observations of Sgr A* during 2007 April 1-11
• Imaging the Supermassive Black Hole Shadow and Jet Base of M87 with the Event Horizon Telescope
• Super-resolution Full Polarimetric Imaging for Radio Interferometry with Sparse Modeling
• Theory and Simulations of Refractive Substructure in Resolved Scatter-Broadened Images
• Persistent Asymmetric Structure of Sagittarius A* on Event Horizon Scales
• Imaging an Event Horizon: Mitigation of Scattering Toward Sagittarius A*
• Probing the magnetic field structure in Sgr A* on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations
• The Submillimeter Polarization of Sgr A*
• Near infrared flares of Sagittarius A*: Importance of near infrared polarimetry
• ALMA and VLA measurements of frequency-dependent time lags in Sagittarius A*: evidence for a relativistic outflow
• SN 1993J VLBI (III): The Evolution of the Radio Shell
• Multiwavelength VLBI observations of Sagittarius A*
• Imaging an Event Horizon: Mitigation of Source Variability of Sagittarius A*
• Detecting Changing Polarization Structures in Sagittarius A* with High Frequency VLBI
• Stochastic Optics: A Scattering Mitigation Framework for Radio Interferometric Imaging
• Fast launch speeds in radio flares, from a new determination of the intrinsic motions of SS 433's jet bolides
• Localizing Sagittarius A* and M87 on Microarcsecond Scales with Millimeter VLBI
• Quantifying Intrinsic Variability of Sagittarius A* using Closure Phase Measurements of the Event Horizon Telescope
• GRMHD simulations of visibility amplitude variability for Event Horizon Telescope images of Sgr A*
• Bayesian techniques for comparing time-dependent GRMHD simulations to variable Event Horizon Telescope observations
• Variability in GRMHD simulations of Sgr A${}^{\ast }$: Implications for EHT closure phase observations
• Observations of the Structure and Dynamics of the Inner M87 Jet
• Relative Astrometry of Compact Flaring Structures in Sgr A* with Polarimetric VLBI
• Detection of multiple velocity components in partially overlapping emitting regions
• Transient Astrophysics with the Square Kilometre Array
• Time Domain Filtering of Resolved Images of Sgr A*
• Assessing the quality of restored images in optical long-baseline interferometry
• Measuring the Direction and Angular Velocity of a Black Hole Accretion Disk via Lagged Interferometric Covariance

Cited by in corpus (49)

• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole
• Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole
• 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
• The mass distribution in the Galactic Centre from interferometric astrometry of multiple stellar orbits
• Interferometric Imaging Directly with Closure Phases and Closure Amplitudes
• Testing General Relativity with the Event Horizon Telescope
• Key Science Goals for the Next-Generation Event Horizon Telescope
• Frankenstein: Protoplanetary disc brightness profile reconstruction at sub-beam resolution with a rapid Gaussian process
• Superradiant evolution of the shadow and photon ring of Sgr A${}^{\star }$
• Photon Ring Autocorrelations
• Variable structures in M87* from space, time and frequency resolved interferometry
• Simulations of imaging the event horizon of Sagittarius A* from space
• Black Hole Shadow as a Test of General Relativity: Quadratic Gravity
• Reference Array and Design Consideration for the next-generation Event Horizon Telescope
• Superresolution Interferometric Imaging with Sparse Modeling Using Total Squared Variation --- Application to Imaging the Black Hole Shadow
• The Varying Kinematics of Multiple Ejecta from the Black Hole X-ray Binary MAXI J1820+070
• Metrics and Motivations for Earth-Space VLBI: Time-Resolving Sgr A* with the Event Horizon Telescope
• Test of Einstein equivalence principle near the Galactic center supermassive black hole
• HI 21cm Cosmology and the Bi-spectrum: Closure Diagnostics in Massively Redundant Interferometric Arrays
• Studying Black Holes on Horizon Scales with VLBI Ground Arrays
• Simulations of M87 and Sgr A* Imaging with the Millimetron Space Observatory on near-Earth orbits
• Silhouettes of invisible black holes
• Selective Dynamical Imaging of Interferometric Data
• Using space-VLBI to probe gravity around Sgr A*
• Black Hole Spin Signature in the Black Hole Shadow of M87 in the Flaring State
• Black hole parameter estimation with synthetic Very Long Baseline Interferometry data from the ground and from space
• Testing General Relativity with the Black Hole Shadow Size and Asymmetry of Sagittarius A*: Limitations from Interstellar Scattering
• Black hole Spin Measurement Based on Time-domain VLBI Observations of Infalling Gas Cloud
• Wideband Super-resolution Imaging in Radio Interferometry via Low Rankness and Joint Average Sparsity Models (HyperSARA)
• Principal Component Analysis as a Tool for Characterizing Black Hole Images and Variability
• To see invisible: image of the event horizon within the black hole shadow
• Using multiobjective optimization to reconstruct interferometric data (I)
• Observing the Shadows of Stellar-Mass Black Holes with Binary Companions
• 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
• VLBI imaging of black holes via second moment regularization
• Imaging the event horizon of M87* from space on different timescales
• Expanding Sgr A* dynamical imaging capabilities with an African extension to the Event Horizon Telescope
• The FHD Polarized Imaging Pipeline: A New Approach to Widefield Interferometric Polarimetry
• SYMBA: An end-to-end VLBI synthetic data generation pipeline
• Prospects of using closure traces directly for imaging in Very Long Baseline Interferometry
• Studying black holes on horizon scales with space-VLBI
• On the prospects of imaging Sagittarius A* from space
• New Views of Black Holes from Computational Imaging
• Characterization of black hole accretion through image moment invariants
• Visible shapes of black holes M87* and SgrA*
• Multiobjective optimization for scattering mitigation and scattering screen reconstruction in VLBI observations of the Galactic Center