Letter to the Editor

Ordered magnetic fields around the 3C 84 central black hole

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: gfparaschos@mpifr-bonn.mpg.de
² Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 702-701, Republic of Korea
³ Institute of Physics, Silesian University in Opava, Bezručovo nám. 13, 746 01 Opava, Czech Republic
⁴ Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁵ Institut de Radioastronomie Millimétrique (IRAM), Avenida Divina Pastora 7, Local 20, 18012 Granada, Spain
⁶ Department of Astrophysics, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University, PO Box 9010 6500 GL Nijmegen, The Netherlands
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⁸ Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
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³¹ Trottier Space Institute at McGill, 3550 rue University, Montréal, QC H3A 2A7, Canada
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³⁶ Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
³⁷ Korea Astronomy and Space Science Institute, Daedeok-daero 776, Yuseong-gu, Daejeon 34055, Republic of Korea
³⁸ University of Science and Technology, Gajeong-ro 217, Yuseong-gu, Daejeon 34113, Republic of Korea
³⁹ Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
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⁴¹ Enrico Fermi Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
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⁴³ Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, NY 14853, USA
⁴⁴ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, PR China
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⁵³ Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Avenue, New York, NY 10010, USA
⁵⁴ Dipartimento di Fisica “E. Pancini”, Universitá di Napoli “Federico II”, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, 80126 Napoli, Italy
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⁵⁸ Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University, Makhanda 6140, South Africa
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⁶⁰ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92195 Meudon, France
⁶¹ JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309, USA
⁶² National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100101, PR China
⁶³ Las Cumbres Observatory, 6740 Cortona Drive, Suite 102, Goleta, CA 93117-5575, USA
⁶⁴ Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
⁶⁵ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
⁶⁶ Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 32-D476, 77 Massachusetts Ave., Cambridge, MA 02142, USA
⁶⁷ Google Research, 355 Main St., Cambridge, MA 02142, USA
⁶⁸ Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Emil-Fischer-Str. 31, 97074 Würzburg, Germany
⁶⁹ Department of History of Science, Harvard University, Cambridge, MA 02138, USA
⁷⁰ Department of Physics, Harvard University, Cambridge, MA 02138, USA
⁷¹ NCSA, University of Illinois, 1205 W. Clark St., Urbana, IL 61801, USA
⁷² Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, R. do Matão, 1226, São Paulo, SP 05508-090, Brazil
⁷³ Dipartimento di Fisica, Universitá degli Studi di Cagliari, SP Monserrato-Sestu km 0.7, 09042 Monserrato, (CA), Italy
⁷⁴ INAF – Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius (CA), Italy
⁷⁵ INFN, sezione di Cagliari, 09042 Monserrato (CA), Italy
⁷⁶ CP3-Origins, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
⁷⁷ Instituto Nacional de Astrofísica, Óptica y Electrónica. Apartado Postal 51 y 216, 72000 Puebla Pue., Mexico
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⁷⁹ Key Laboratory for Research in Galaxies and Cosmology, Chinese Academy of Sciences, Shanghai 200030, PR China
⁸⁰ Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan
⁸¹ Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
⁸² Trottier Space Institute at McGill, 3550 rue University, Montréal, QC H3A 2A7, Canada
⁸³ NOVA Sub-mm Instrumentation Group, Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
⁸⁴ Department of Astronomy, School of Physics, Peking University, Beijing 100871, PR China
⁸⁵ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, PR China
⁸⁶ Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
⁸⁷ The Institute of Statistical Mathematics, 10-3 Midori-cho, Tachikawa, Tokyo 190-8562, Japan
⁸⁸ Department of Statistical Science, The Graduate University for Advanced Studies (SOKENDAI), 10-3 Midori-cho, Tachikawa, Tokyo 190-8562, Japan
⁸⁹ , 5-1-5 Kashiwanoha, Kashiwa 277-8583, Japan
⁹⁰ Leiden Observatory, Leiden University, Postbus 2300, 9513 RA Leiden, The Netherlands
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⁹³ Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave., Boston, MA 02215, USA
⁹⁴ Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582, Japan
⁹⁵ Joint Institute for VLBI ERIC (JIVE), Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
⁹⁶ Kogakuin University of Technology & Engineering, Academic Support Center, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan
⁹⁷ Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata 950-2181, Japan
⁹⁸ Physics Department, National Sun Yat-Sen University, No. 70, Lien-Hai Road, Kaosiung City, 80424 Taiwan, R.O.C.
⁹⁹ National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719, USA
¹⁰⁰ Department of Physics, The Chinese University of Hong Kong, Shatin, N. T., Hong Kong
¹⁰¹ School of Astronomy and Space Science, Nanjing University, Nanjing 210023, PR China
¹⁰² Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University, Nanjing 210023, PR China
¹⁰³ INAF-Istituto di Radioastronomia, Via P. Gobetti 101, 40129 Bologna, Italy
¹⁰⁴ INAF-Istituto di Radioastronomia & Italian ALMA Regional Centre, Via P. Gobetti 101, 40129 Bologna, Italy
¹⁰⁵ Department of Physics, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617 Taiwan, R.O.C.
¹⁰⁶ Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia 58089, Mexico
¹⁰⁷ Yunnan Observatories, Chinese Academy of Sciences, 650011 Kunming, Yunnan Province, PR China
¹⁰⁸ Center for Astronomical Mega-Science, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, PR China
¹⁰⁹ Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, 650011 Kunming, PR China
¹¹⁰ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
¹¹¹ Gravitation and Astroparticle Physics Amsterdam (GRAPPA) Institute, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
¹¹² Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544, USA
¹¹³ Science Support Office, Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
¹¹⁴ School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China
¹¹⁵ Astronomy Department, Universidad de Concepción, Casilla 160-C, Concepción, Chile
¹¹⁶ National Institute of Technology, Hachinohe College, 16-1 Uwanotai, Tamonoki, Hachinohe City, Aomori 039-1192, Japan
¹¹⁷ Research Center for Astronomy, Academy of Athens, Soranou Efessiou 4, 115 27 Athens, Greece
¹¹⁸ Department of Physics, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085, USA
¹¹⁹ Physics Department, Washington University, CB 1105, St. Louis, MO 63130, USA
¹²⁰ School of Physics, Georgia Institute of Technology, 837 State St NW, Atlanta, GA 30332, USA
¹²¹ Department of Astronomy and Space Science, Kyung Hee University, 1732, Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104, Republic of Korea
¹²² Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada
¹²³ Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada
¹²⁴ Canadian Institute for Advanced Research, 180 Dundas St West, Toronto, ON M5G 1Z8, Canada
¹²⁵ Radio Astronomy Laboratory, University of California, Berkeley, CA 94720, USA
¹²⁶ Institute of Astrophysics, Foundation for Research and Technology – Hellas, Voutes, 7110 Heraklion, Greece
¹²⁷ Department of Physics, National Taiwan Normal University, No. 88, Sec. 4, Tingzhou Rd., Taipei, 116 Taiwan, R.O.C.
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¹²⁹ Finnish Centre for Astronomy with ESO, University of Turku, 20014 Turku, Finland
¹³⁰ Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
¹³¹ Gemini Observatory/NSF NOIRLab, 670 N. A’ohōkūPlace, Hilo, HI 96720, USA
¹³² Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, 60438 Frankfurt, Germany
¹³³ School of Mathematics, Trinity College, Dublin 2, Ireland
¹³⁴ Department of Physics, University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7, Canada
¹³⁵ Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
¹³⁶ Hiroshima Astrophysical Science Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
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¹³⁸ Department of Astronomy, Yonsei University, Yonsei-ro 50, Seodaemun-gu, 03722 Seoul, Republic of Korea
¹³⁹ National Biomedical Imaging Center, Peking University, Beijing 100871, PR China
¹⁴⁰ College of Future Technology, Peking University, Beijing 100871, PR China
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¹⁴⁶ Physics Department, Brandeis University, 415 South Street, Waltham, MA 02453, USA
¹⁴⁷ Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Turku, Finland
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¹⁴⁹ School of Natural Sciences, Institute for Advanced Study, 1 Einstein Drive, Princeton, NJ 08540, USA
¹⁵⁰ School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
¹⁵¹ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
¹⁵² School of Astronomy and Space Sciences, University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, PR China
¹⁵³ Astronomy Department, University of Science and Technology of China, Hefei 230026, PR China
¹⁵⁴ Department of Physics and Astronomy, Michigan State University, 567 Wilson Rd, East Lansing, MI 48824, USA

Received: 18 October 2023
Accepted: 3 December 2023

Abstract

Context. 3C 84 is a nearby radio source with a complex total intensity structure, showing linear polarisation and spectral patterns. A detailed investigation of the central engine region necessitates the use of very-long-baseline interferometry (VLBI) above the hitherto available maximum frequency of 86 GHz.

Aims. Using ultrahigh resolution VLBI observations at the currently highest available frequency of 228 GHz, we aim to perform a direct detection of compact structures and understand the physical conditions in the compact region of 3C 84.

Methods. We used Event Horizon Telescope (EHT) 228 GHz observations and, given the limited (u, v)-coverage, applied geometric model fitting to the data. Furthermore, we employed quasi-simultaneously observed, ancillary multi-frequency VLBI data for the source in order to carry out a comprehensive analysis of the core structure.

Results. We report the detection of a highly ordered, strong magnetic field around the central, supermassive black hole of 3C 84. The brightness temperature analysis suggests that the system is in equipartition. We also determined a turnover frequency of ν_m = (113 ± 4) GHz, a corresponding synchrotron self-absorbed magnetic field of B_SSA = (2.9 ± 1.6) G, and an equipartition magnetic field of B_eq = (5.2 ± 0.6) G. Three components are resolved with the highest fractional polarisation detected for this object (m_net = (17.0 ± 3.9)%). The positions of the components are compatible with those seen in low-frequency VLBI observations since 2017–2018. We report a steeply negative slope of the spectrum at 228 GHz. We used these findings to test existing models of jet formation, propagation, and Faraday rotation in 3C 84.

Conclusions. The findings of our investigation into different flow geometries and black hole spins support an advection-dominated accretion flow in a magnetically arrested state around a rapidly rotating supermassive black hole as a model of the jet-launching system in the core of 3C 84. However, systematic uncertainties due to the limited (u, v)-coverage, however, cannot be ignored. Our upcoming work using new EHT data, which offer full imaging capabilities, will shed more light on the compact region of 3C 84.