Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
Creators: name: Algaba, J. C.
name: Anczarski, J.
name: Asada, K.
name: Baloković, M.
name: Chandra, S.
name: Cui, Y.-Z.
name: Falcone, A. D.
name: Giroletti, M.
name: Goddi, C.
name: Hada, K.
name: Haggard, D.
name: Jorstad, S.
name: Kaur, A.
name: Kawashima, T.
name: Keating, G.
name: Kim, J.-Y.
name: Kino, M.
name: Komossa, S.
name: Kravchenko, E. V.
name: Krichbaum, T. P.
name: Lee, S.-S.
name: Lu, R.-S.
name: Lucchini, M.
name: Markoff, S.
name: Neilsen, J.
name: Nowak, M. A.
name: Park, J.
name: Principe, G.
name: Ramakrishnan, V.
name: Reynolds, M. T.
name: Sasada, M.
name: Savchenko, S. S.
name: Williamson, K. E.
name: Akiyama, Kazunori
name: Alberdi, Antxon
name: Alef, Walter
name: Anantua, Richard
name: Azulay, Rebecca
name: Baczko, Anne-Kathrin
name: Ball, David
name: Barrett, John
name: Bintley, Dan
name: Benson, Bradford A.
name: Blackburn, Lindy
name: Blundell, Raymond
name: Boland, Wilfred
name: Bouman, Katherine L.
name: Bower, Geoffrey C.
name: Boyce, Hope
name: Bremer, Michael
name: Brinkerink, Christiaan D.
name: Brissenden, Roger
name: Britzen, Silke
name: Broderick, Avery E.
name: Broguiere, Dominique
name: Bronzwaer, Thomas
name: Byun, Do-Young
name: Carlstrom, John E.
name: Chael, Andrew
name: Chan, Chi-Kwan
name: Chatterjee, Shami
name: Chatterjee, Koushik
name: Chen, Ming-Tang
name: Chen, Yongjun
name: Chesler, Paul M.
name: Cho, Ilje
name: Christian, Pierre
name: Conway, John E.
name: Cordes, James M.
name: Crawford, Thomas M.
name: Crew, Geoffrey B.
name: Cruz-Osorio, Alejandro
name: Davelaar, Jordy
name: De Laurentis, Mariafelicia
name: Deane, Roger
name: Dempsey, Jessica
name: Desvignes, Gregory
name: Dexter, Jason
name: Doeleman, Sheperd S.
name: Eatough, Ralph P.
name: Falcke, Heino
name: Farah, Joseph
name: Fish, Vincent L.
name: Fomalont, Ed
name: Ford, H. Alyson
name: Fraga-Encinas, Raquel
name: Friberg, Per
name: Fromm, Christian M.
name: Fuentes, Antonio
name: Galison, Peter
name: Gammie, Charles F.
name: García, Roberto
name: Gentaz, Olivier
name: Georgiev, Boris
name: Gold, Roman
name: Gómez, José L.
name: Gómez-Ruiz, Arturo I.
name: Gu, Minfeng
name: Gurwell, Mark
name: Hecht, Michael H.
Publisher: name: Humboldt-Universität zu Berlin
Year: 2021
Subjects: subject: Active galactic nuclei
subject: Radio cores
subject: Low-luminosity active galactic nuclei
subject: High energy astrophysics
subject: Astrophysical black holes
subject: Accretion
subject: 520 Astronomie und zugeordnete Wissenschaften
subject: 530 Physik

description: 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 ∼6.5 × 109 M ⊙. 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 γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-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.