Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign

Abstract

In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass approximately 6.5 x 10^9 M_solar. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous gamma-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the gamma-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded.

43 pages, 19 figures, 10 tables; complete author list available in manuscript; The Astrophysical Journal Letters, 2021, 911, L11; publication doi: 3847/2041-8213/abef71, data doi: 10.25739/mhh2-cw46

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• Key Science Goals for the Next-Generation Event Horizon Telescope
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• Reference Array and Design Consideration for the next-generation Event Horizon Telescope
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• Separating Astrophysics and Geometry in Black Hole Images
• Black Hole Polarimetry I: A Signature of Electromagnetic Energy Extraction
• Images of magnetospheric reconnection-powered radiation around supermassive black holes
• Spinning black holes magnetically connected to a Keplerian disk -- Magnetosphere, reconnection sheet, particle acceleration and coronal heating
• Broadband Multi-wavelength Properties of M87 during the 2018 EHT Campaign including a Very High Energy Flaring Episode
• Positron Effects on Polarized Images and Spectra from Jet and Accretion Flow Models of M87* and Sgr A*
• Spectral analysis of a parsec-scale jet in M87: Observational constraint on the magnetic field strengths in the jet
• Horizonless spacetimes as seen by present and next-generation Event Horizon Telescope arrays
• Hadronuclear interactions in the jet of low TeV luminosity AGN: Implications for the low-state very-high-energy gamma-ray emission
• M87: a cosmic laboratory for deciphering black hole accretion and jet formation
• Magnetic Reconnection in Black-Hole Magnetospheres: Lepton Loading into Jets, Superluminal Radio Blobs, and Multi-wavelength Flares
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• Implications from the velocity profile of the M87 jet: a possibility of a slowly rotating black hole magnetosphere
• Formation of episodic jets and associated flares from black hole accretion systems
• Hybrid mapping of the Black Hole Shadow in M87
• Multi-wavelength Variability of Sagittarius A* in July 2019
• The response of black hole spark gaps to external changes: A production mechanism of rapid TeV flares?
• Overview of the Observing System and Initial Scientific Accomplishments of the East Asian VLBI Network (EAVN)
• Probing Plasma Physics with Spectral Index Maps of Accreting Black Holes on Event Horizon Scales
• Curvature in the very-high energy gamma-ray spectrum of M87
• Testing the linear relationship between black hole mass and variability timescale in low-luminosity AGN at submillimeter wavelengths
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• RAIKOU: A General Relativistic, Multi-wavelength Radiative Transfer Code
• Detection of very high-energy gamma-ray emission from the radio galaxy M87 with LHAASO
• Lepto-hadronic jet-disc model for the multi-wavelength SED of M87
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• Effects of Hydrogen vs. Helium on Electromagnetic Black Hole Observables
• Multi-Frequency Models of Black Hole Photon Rings from Low-Luminosity Accretion Disks
• Observational Signatures of Black Hole Accretion: Rotating vs. Spherical Flows with Tilted Magnetic Fields
• Co-precession of a curved jet and compact accretion disk in M87
• Constraining the cosmic-ray pressure in the inner Virgo Cluster using H.E.S.S. observations of M 87
• High-energy Gamma-rays from Magnetically Arrested Disks in Nearby Radio Galaxies
• Observational Constraints on Direct Electron Heating in the Hot Accretion Flows in Sgr A* and M87*
• Deep learning inference with the Event Horizon Telescope II. The Zingularity framework for Bayesian artificial neural networks
• The X-shaped radio galaxy J0725+5835 is associated with an AGN pair
• Super-Resolved Image of M87 Observed with East Asian VLBI Network
• The Japanese Vision for the Black Hole Explorer Mission
• On the sub-parsec scale core composition of FR 0 radio galaxies
• The year-scale X-ray variations in the core of M87
• Measuring black hole spins with x-ray reflection spectroscopy: A GRMHD outlook
• Constraining eV-scale axion-like particle dark matter: insights from the M87 Galaxy
• The X-ray variation of M81* resolved by Chandra and NuSTAR
• Measuring the properties of homogeneous turbulence in curved spacetimes
• H.E.S.S.: The High Energy Stereoscopic System
• Assessing the Role of Intrinsic Variability in Black Hole Parameter Inference using Multi-Epoch EHT Data
• The infrared jet of M87 observed with JWST
• The Bardeen-Petterson Effect as an Observable Support for the Blanford-Payne Process Black Hole Jet Production
• Explaining the Origin of TeV Gamma Rays from M87 During High and Low States
• The Discovery of an Active Wind from the Milky Way's Black Hole
• Constraints on High-Frequency Gravitational Waves from Graviton-Photon Conversion in the M87 Galaxy
• Transverse Oscillations and Wave Propagation in the Magnetically Dominated M87 Jet
• Multiwavelength View of the M87 Black Hole Captured by the Event Horizon Telescope
• Multi-wavelength observations of the Blazar 4C +28.07
• Millimeter-VLBI observations of low-luminosity active galactic nuclei with source-frequency phase-referencing
• PATOKA: Simulating Electromagnetic Observables of Black Hole Accretion
• Ergomagnetosphere, Ejection Disc, Magnetopause in M87. I Global Flow of Mass, Angular Momentum, Energy and Current
• Investigating the Disk-Jet Structure in M87 through Flux Separation in the Linear and Circular Polarization Images
• A revised view of the linear polarization in the subparsec core of M87 at 7 mm
• Impact of non-thermal particles on the spectral and structural properties of M87