First M87 Event Horizon Telescope Results. III. Data Processing and Calibration

Abstract

We present the calibration and reduction of Event Horizon Telescope (EHT) 1.3mm radio wavelength observations of the supermassive black hole candidate at the center of the radio galaxy M87 and the quasar 3C 279, taken during the 2017 April 5-11 observing campaign. These global very long baseline interferometric observations include for the first time the highly sensitive Atacama Large Millimeter/submillimeter Array (ALMA); reaching an angular resolution of 25 micro-as, with characteristic sensitivity limits of ~1 mJy on baselines to ALMA and ~10 mJy on other baselines. The observations present challenges for existing data processing tools, arising from the rapid atmospheric phase fluctuations, wide recording bandwidth, and highly heterogeneous array. In response, we developed three independent pipelines for phase calibration and fringe detection, each tailored to the specific needs of the EHT. The final data products include calibrated total intensity amplitude and phase information. They are validated through a series of quality assurance tests that show consistency across pipelines and set limits on baseline systematic errors of 2% in amplitude and 1 degree in phase. The M87 data reveal the presence of two nulls in correlated flux density at ~3.4 and ~8.3 giga-lambda and temporal evolution in closure quantities, indicating intrinsic variability of compact structure on a timescale of days, or several light-crossing times for a few billion solar-mass black hole. These measurements provide the first opportunity to image horizon-scale structure in M87.

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• First polarization study of the M87 jet and active galactic nuclei at submillimeter wavelengths with ALMA
• Comment on "Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A*"
• Strong gravitational lensing of rotating regular black holes in non-minimally coupled Einstein-Yang-Mills theory
• Gravitational lens on a static optical constant-curvature background: Its application to Weyl gravity model
• A regular metric does not ensure the regularity of spacetime
• Modified Kerr black holes surrounded by dark matter spike
• Anisotropies of Diffusive Ultra-high Energy Cosmic Rays in $f(R)$ Gravity Theory
• Extended Geometric Trinity of Gravity
• Remarks on the light ring images and the optical appearance of hairy black holes in Einstein-Maxwell-dilaton gravity
• Expanding Sgr A* dynamical imaging capabilities with an African extension to the Event Horizon Telescope
• Black Holes in Lorentz-Violating Gravity: Thermodynamics, Geometry, and Particle Dynamics
• Deep learning inference with the Event Horizon Telescope III. Zingularity results from the 2017 observations and predictions for future array expansions
• Optical appearance of the Schwarzschild black hole in the string cloud context
• Imaging the event horizon of M87* from space on different timescales
• Nondivergent deflection of light around a photon sphere of a compact object
• Shadows and photon spheres in static and rotating traversable wormholes
• Probing Accretion Turbulence in the Galactic Center with EHT Polarimetry
• Correspondence between two gravitational lens equations in a static and spherically symmetric spacetime
• On optical appearance of Einstein-Maxwell-Æther black holes surrounded by various accretions
• Fate of initially bound timelike geodesics in spherical boson stars
• Effect of matter geometry on low angular momentum black hole accretion in the Kerr metric
• Determining parameters of a spherical black hole with a thin accretion disk by observing its shadow
• Semi-analytic studies of accretion disk and magnetic field geometry in M87*
• The Shadow of Supertranslated Schwarzschild Black Hole
• Topological Data Analysis of Black Hole Images
• Effect of quantum deformed black hole on BH shadow in two-dimensional Dilaton gravity
• Gravitational analog of the canonical acoustic black hole in Einstein-scalar-Gauss-Bonnet theory
• Deep learning inference with the Event Horizon Telescope II. The Zingularity framework for Bayesian artificial neural networks
• Deep learning inference with the Event Horizon Telescope I. Calibration improvements and a comprehensive synthetic data library
• SYMBA: An end-to-end VLBI synthetic data generation pipeline
• Strong-field gravitational lensing by black holes
• Fractal signatures of non-Kerr spacetimes in the shadow of light-ring bifurcations
• Gödel-type Solutions in Cubic Galileon Gravity
• The Japanese Vision for the Black Hole Explorer Mission
• The Black Hole Explorer: Operating a Hybrid Observatory
• A probabilistic approach to phase calibration: I. Effects of source structure on fringe-fitting
• Traversable wormholes with multiple unstable critical curves
• The Effects of Resolution on Black Hole Accretion Simulations of Jets
• Impact of the nonthermal electron radiation effects on the horizon scale image structure of Sagittarius A*
• Quantumness near the Schwarzschild black hole based on W-state
• Interferometric Image Reconstruction using Closure Invariants and Machine Learning
• Shadow of Kerr black hole surrounded by a cloud of strings in Rastall gravity and constraints from M87*
• Signatures of regular black holes from the quasar continuum spectrum
• Scalar absorption cross section of rotating black holes with tidal charge
• Efficient gravitational lens optical scalars calculation of black holes with angular momentum
• Not all spacetime coordinates for general-relativistic ray tracing are created equal
• Overlapping of photon rings in black hole imaging
• Strong Lensing Effect and Quasinormal Modes of Oscillations of Black Holes in $\mathbf{f}(\mathbf{R},\mathbf{T})$ Gravity Theory
• Interferometric Closure Phase Uncertainties in the Low Signal-to-Noise Ratio Regime
• Origin of the ring ellipticity in the black hole images of M87*
• Magnetic Suppression of Cosmic Rays' Flux in $\mathbf{f}(\mathbf{R})$ and $\mathbf{f}(\mathbf{Q})$ Theories of Gravity
• Optical images of the Kerr-Sen black hole and thin accretion disk
• Shadowless rapidly rotating yet not ultraspinning Kerr-AdS${}_4$ and Kerr-Newman-AdS${}_4$ black holes
• Shadows of a generic class of spherically symmetric, static spacetimes
• Dynamics of scalar hair with self-interactions around a Schwarzchild black hole
• The surface geometry and shadow of a Schwarzschild black hole with halo
• A proof-of-concept neural network for inferring parameters of a black hole from partial interferometric images of its shadow
• Is it possible to distinguish between different black hole solutions using the Shapiro time delay?
• Regular black hole solutions in $(2+1)$-dimensional $f(R,T)$ gravity coupled to nonlinear electrodynamics
• A full waveform model for arbitrarily axis-symmetric black hole mergers
• Superradiance scattering of scalar, electromagnetic, and gravitational fields and thin accretion disk around non-commutating Kerr black hole
• Shadow of higher dimensional collapsing dark star and blackhole
• Determining parameters of Kerr black holes at finite distance by shadow observation
• Shadow of quadrupole-deformed compact objects in a local dark matter shell
• Constraining eV-scale axion-like particle dark matter: insights from the M87 Galaxy
• Kiselev-inspired Wormholes
• Spontaneous Vectorization in the Einstein-Maxwell-Vector Model
• Shadow of axisymmetric, stationary and asymptotically flat black holes in the presence of plasma
• Non-thermal Synchrotron Emission and Polarization Signatures during Black Hole Flux Eruptions
• Accretion Process as a Probe of Extra Dimensions in MOG Compact Object Spacetimes
• Towards an astronomical use of new-generation geodetic observations. I. From the correlator to full-polarization images
• Quasinormal Modes and Shadows of Black Holes in Infinite Derivative Theory of Gravity
• Shadow and near-horizon characteristics of the acoustic charged black hole in curved spacetime
• Limiting the Yukawa Gravity through the Black Hole Shadows of Sgr A* and M87*
• Gravitational wave pulse and memory effects for hairy Kiselev black hole and its analogy with Bondi-Sachs formalism
• Screen chaotic motion by Shannon entropy in curved spacetimes
• Determining parameters of Kerr-Newman black holes by shadow observation from finite distance and spatial infinity
• Detecting Black Hole Occultations by Stars with Space Interferometric Telescopes
• rPICARD: A CASA-based Calibration Pipeline for VLBI Data. Calibration and imaging of 7 mm VLBA observations of the AGN jet in M87
• Strong gravitational lensing of a five-dimensional charged, equally rotating black hole with a cosmological constant
• Effect of Earth's Oblateness on Black Hole Imaging Through Earth-Space and Space-Space VLBI
• Kilogauss magnetic field and jet dynamics in the quasar NRAO 530
• Charge constraint on M87* with twisted light
• Deciphering signatures of Kerr-Sen black holes in presence of plasma from the Event Horizon Telescope data
• A Red-Noise Eigenbasis for the Reconstruction of Blobby Images
• Microlensing Black Hole Shadows
• Noncommutative information is revealed from the static detector outside the black hole
• Conic Sections on the Sky: Shadows of Linearly Superrotated Black Holes
• Explaining the Origin of TeV Gamma Rays from M87 During High and Low States
• Constraints on High-Frequency Gravitational Waves from Graviton-Photon Conversion in the M87 Galaxy
• Shadows cast by a class of rotating black bounces with an anisotropic fluid
• Exploring black holes with multiple photon spheres by interferometric signatures
• Perturbations of Einstein--Maxwell--phantom spacetime: Instabilities of charged Ellis--Bronnikov wormholes and quasinormal modes of black holes
• Characterization of black hole accretion through image moment invariants
• Shadow constraints of charged black hole with scalar hair and gravitational waves from extreme mass ratio inspirals
• Thin accretion disk around Schwarzschild-like black hole in bumblebee gravity
• Images of the accretion disk in Hybrid metric-Palatini gravity
• Tests for the existence of horizon through gravitational waves from a small binary in the vicinity of a massive object
• Polish Doughnuts around Scalarized Kerr Black Holes
• General relativistic radiation transport: Implications for VLBI/EHT observations of AGN discs, winds and jets
• Decoding a black hole metric from the interferometric pattern of the relativistic images of a compact source
• The science case and challenges of space-borne sub-millimeter interferometry
• A revised view of the linear polarization in the subparsec core of M87 at 7 mm
• How narrow is the M87* ring? I. The choice of closure likelihood function
• High Resolution Imaging of a Black Hole Shadow with Millimetron Orbit around Lagrange Point L2
• Bardeen-Kiselev black hole with cosmological constant
• Probing the disk-jet coupling in M87
• PATOKA: Simulating Electromagnetic Observables of Black Hole Accretion
• Shadows of naked singularities and superspinars related to the revisited Kerr-de Sitter spacetimes
• Rotating black hole shadows in metric-affine bumblebee gravity
• Visible shapes of black holes M87* and SgrA*
• Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron. V. Space and ground millimeter-VLBI imaging of OJ 287
• Perturbative Renormalisation Group Improved Black Hole Solution and its Quasinormal Modes
• Shaving off soft hairs and the black hole image memory effect
• Optical appearance of regularized compact objects without an exterior photon sphere
• Photon Ring Symmetries in Simulated Linear Polarization Images of Messier 87*
• Parameter Inference of Black Hole Images using Deep Learning in Visibility Space
• Scattering by deformed black holes
• Quasar continuum spectrum disfavors black holes with a magnetic monopole charge
• Typical reconstruction limit and phase transition of maximum entropy method
• Ultra-high energy cosmic rays with UFA-15 source model in Bumblebee gravity theory
• Modelling Cosmic Rays Flux with Pierre Auger and Telescope Array Data in $\mathbf{f}(\mathbf{R})$ and $\mathbf{f}(\mathbf{Q})$ Theories of Gravity
• What are the parities of photon-ring images near a black hole?
• Images of black holes viewed by distant observer
• Gravitational wave memory in wormhole spacetimes
• Charged spherically symmetric black holes in the Lyra geometry and a preliminary investigation on the overcharging process
• The eye of the storm: A regular Kerr black hole
• Photon Ring Dimming as a Signature of Photon-Axion Conversion in Janis-Newman-Winicour Naked Singularity
• P-stars in the gravitational wave era
• Multiobjective optimization for scattering mitigation and scattering screen reconstruction in VLBI observations of the Galactic Center