First M87 Event Horizon Telescope Results. II. Array and Instrumentation

Abstract

The Event Horizon Telescope (EHT) is a very long baseline interferometry (VLBI) array that comprises millimeter- and submillimeter-wavelength telescopes separated by distances comparable to the diameter of the Earth. At a nominal operating wavelength of ~1.3 mm, EHT angular resolution (lambda/D) is ~25 micro-as, which is sufficient to resolve nearby supermassive black hole candidates on spatial and temporal scales that correspond to their event horizons. With this capability, the EHT scientific goals are to probe general relativistic effects in the strong-field regime and to study accretion and relativistic jet formation near the black hole boundary. In this Letter we describe the system design of the EHT, detail the technology and instrumentation that enable observations, and provide measures of its performance. Meeting the EHT science objectives has required several key developments that have facilitated the robust extension of the VLBI technique to EHT observing wavelengths and the production of instrumentation that can be deployed on a heterogeneous array of existing telescopes and facilities. To meet sensitivity requirements, high-bandwidth digital systems were developed that process data at rates of 64 gigabit/s, exceeding those of currently operating cm-wavelength VLBI arrays by more than an order of magnitude. Associated improvements include the development of phasing systems at array facilities, new receiver installation at several sites, and the deployment of hydrogen maser frequency standards to ensure coherent data capture across the array. These efforts led to the coordination and execution of the first Global EHT observations in 2017 April, and to event-horizon-scale imaging of the supermassive black hole candidate in M87.

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• First M87 Event Horizon Telescope Results. III. Data Processing and Calibration
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• Super-resolution Full Polarimetric Imaging for Radio Interferometry with Sparse Modeling
• Imaging an Event Horizon: Mitigation of Scattering Toward Sagittarius A*
• Radio observations of active galactic nuclei with mm-VLBI
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• Evaluation of the ALMA Prototype Antennas
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• Generalised warped disk equations
• Adapting a Cryogenic Sapphire Oscillator for Very Long Baseline Interferometry
• High gas fraction in a CO-selected main-sequence galaxy at $z>3$
• Quantifying Intrinsic Variability of Sagittarius A* using Closure Phase Measurements of the Event Horizon Telescope
• SPIRE Spectroscopy of Early Type Galaxies
• 3.5-Year Monitoring of 225 GHz Opacity at the Summit of Greenland

Cited by in corpus (25)

• 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. III. Data Processing and Calibration
• Black Hole Shadows, Photon Rings, and Lensing Rings
• Magnetically charged black holes from non-linear electrodynamics and the Event Horizon Telescope
• The Shadow of a Spherically Accreting Black Hole
• Lensing by Kerr Black Holes
• Asymptotic safety casts its shadow
• Higher order corrections to deflection angle of massive particles and light rays in plasma media for stationary spacetimes using the Gauss-Bonnet theorem
• The Surprisingly Small Impact of Magnetic Fields On The Inner Accretion Flow of Sagittarius A* Fueled By Stellar Winds
• Kinematics of the M87 jet in the collimation zone: gradual acceleration and velocity stratification
• Calibration of ALMA as a phased array: ALMA observations during the 2017 VLBI campaign
• Sparse Modeling in Quantum Many-Body Problems
• Wideband 67-116 GHz receiver development for ALMA Band 2
• Observational signature of a near-extremal Kerr-Sen black hole in the heterotic string theory
• Black Hole Spin Signature in the Black Hole Shadow of M87 in the Flaring State
• Black hole Spin Measurement Based on Time-domain VLBI Observations of Infalling Gas Cloud
• Constraining a black hole companion for M87* through imaging by the Event Horizon Telescope
• Exploring the Morphology and Origins of the 4C 38.41 Jet
• Photon Emission Near Myers-Perry Black Holes in the Large Dimension Limit
• Prospects for the characterization of the VHE emission from the Crab Nebula and Pulsar with the Cherenkov Telescope Array
• Efficient gravitational lens optical scalars calculation of black holes with angular momentum
• rPICARD: A CASA-based Calibration Pipeline for VLBI Data. Calibration and imaging of 7 mm VLBA observations of the AGN jet in M87
• Millimeter-wave Monitoring of Active Galactic Nuclei with the Africa Millimetre Telescope