Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution^⋆

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: jykim@mpifr-bonn.mpg.de
² Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, ON N2L 2Y5, Canada
³ Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
⁴ Waterloo Centre for Astrophysics, University of Waterloo, Waterloo, ON N2L 3G1, Canada
⁵ Black Hole Initiative at Harvard University, 20 Garden Street, Cambridge, MA 02138, USA
⁶ Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
⁷ Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
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⁹ Princeton Center for Theoretical Science, Jadwin Hall, Princeton University, Princeton, NJ 08544, USA
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¹² Massachusetts Institute of Technology Haystack Observatory, 99 Millstone Road, Westford, MA 01886, USA
¹³ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁴ Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave., Boston, MA 02215, USA
¹⁵ Astronomical Institute, St. Petersburg University, Universitetskij pr., 28, Petrodvorets 198504, St.Petersburg, Russia
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²⁰ Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
²¹ Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, AS/NTU No. 1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan, R.O.C.
²² Departament d’Astronomia i Astrofísica, Universitat de València, C. Dr. Moliner 50, 46100 Burjassot, València, Spain
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²⁸ Korea Astronomy and Space Science Institute, Daedeok-daero 776, Yuseong-gu, Daejeon 34055, Republic of Korea
²⁹ University of Science and Technology, Gajeong-ro 217, Yuseong-gu, Daejeon 34113, Republic of Korea
³⁰ Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
³¹ Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
³² Department of Physics, University of Chicago, 5720 South Ellis Avenue, Chicago, IL 60637, USA
³³ Enrico Fermi Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
³⁴ Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, NY 14853, USA
³⁵ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
³⁶ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, PR China
³⁷ Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210008, PR China
³⁸ Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 43992 Onsala, Sweden
³⁹ Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan
⁴⁰ Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
⁴¹ Dipartimento di Fisica “E. Pancini”, Universitá di Napoli “Federico II”, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, 80126 Napoli, Italy
⁴² Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
⁴³ INFN Sez. di Napoli, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, 80126 Napoli, Italy
⁴⁴ Department of Physics, University of Pretoria, Lynnwood Road, Hatfield, Pretoria 0083, South Africa
⁴⁵ Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University, Grahamstown 6140, South Africa
⁴⁶ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92195 Meudon, France
⁴⁷ JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309, USA
⁴⁸ Department of History of Science, Harvard University, Cambridge, MA 02138, USA
⁴⁹ Department of Physics, Harvard University, Cambridge, MA 02138, USA
⁵⁰ Department of Physics, University of Illinois, 1110 West Green St, Urbana, IL 61801, USA
⁵¹ Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801, USA
⁵² Leiden Observatory – Allegro, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
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⁵⁴ CONACYT-Instituto Nacional de Astrofísica, Óptica y Electrónica. Apartado Postal 51 y 216, 72000 Puebla, PUE, México
⁵⁵ Key Laboratory for Research in Galaxies and Cosmology, Chinese Academy of Sciences, Shanghai 200030, PR China
⁵⁶ NOVA Sub-mm Instrumentation Group, Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
⁵⁷ Department of Astronomy, School of Physics, Peking University, Beijing 100871, PR China
⁵⁸ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, PR China
⁵⁹ Instituto Nacional de Astrofísica, Óptica y Electrónica. Apartado Postal 51 y 216, 72000 Puebla, PUE, México
⁶⁰ The Institute of Statistical Mathematics, 10-3 Midori-cho, Tachikawa, Tokyo 190-8562, Japan
⁶¹ Department of Statistical Science, The Graduate University for Advanced Studies (SOKENDAI), 10-3 Midori-cho, Tachikawa, Tokyo 190-8562, Japan
⁶² Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8583, Japan
⁶³ ASTRAVEO LLC, PO Box 1668, MA 01931, USA
⁶⁴ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstr. 1, 85748 Garching, Germany
⁶⁵ Joint Institute for VLBI ERIC (JIVE), Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
⁶⁶ Kogakuin University of Technology & Engineering, Academic Support Center, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan
⁶⁷ Physics Department, National Sun Yat-Sen University, No. 70, Lien-Hai Rd, Kaosiung City 80424, Taiwan, R.O.C.
⁶⁸ National Optical Astronomy Observatory, 950 North Cherry Ave., Tucson, AZ 85719, USA
⁶⁹ Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Shijingshan District, Beijing, PR China
⁷⁰ School of Astronomy and Space Science, Nanjing University, Nanjing 210023, PR China
⁷¹ Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University, Nanjing 210023, PR China
⁷² Italian ALMA Regional Centre, INAF-Istituto di Radioastronomia, Via P. Gobetti 101, 40129 Bologna, Italy
⁷³ Department of Physics, National Taiwan University, No.1, Sect.4, Roosevelt Rd., Taipei 10617, Taiwan, R.O.C.
⁷⁴ Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia 58089, México
⁷⁵ Instituto de Astronomía, Universidad Nacional Autónoma de México, CDMX 04510, México
⁷⁶ Yunnan Observatories, Chinese Academy of Sciences, 650011 Kunming, Yunnan Province, PR China
⁷⁷ Center for Astronomical Mega-Science, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, PR China
⁷⁸ Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, 650011 Kunming, PR China
⁷⁹ Gravitation Astroparticle Physics Amsterdam (GRAPPA) Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
⁸⁰ School of Natural Sciences, Institute for Advanced Study, 1 Einstein Drive, Princeton, NJ 08540, USA
⁸¹ Astronomy Department, Universidad de Concepción, Casilla 160-C, Concepción, Chile
⁸² Department of Astronomy, University of Massachusetts, 01003 Amherst, MA, USA
⁸³ Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
⁸⁴ Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada
⁸⁵ Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada
⁸⁶ Canadian Institute for Advanced Research, 180 Dundas St West, Toronto, ON M5G 1Z8, Canada
⁸⁷ Radio Astronomy Laboratory, University of California, Berkeley, CA 94720, USA
⁸⁸ Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544, USA
⁸⁹ Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Avenue, New York, NY 10010, USA
⁹⁰ CCS-2, Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM 87545, USA
⁹¹ Center for Theoretical Astrophysics, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
⁹² Instituto de Radioastronomía Milimétrica, IRAM, Avenida Divina Pastora 7, Local 20, 18012 Granada, Spain
⁹³ Hiroshima Astrophysical Science Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
⁹⁴ Department of Astronomy, Yonsei University, Yonsei-ro 50, Seodaemun-gu 03722, Seoul, Republic of Korea
⁹⁵ Netherlands Organisation for Scientific Research (NWO), Postbus 93138, 2509 AC Den Haag, The Netherlands
⁹⁶ Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578, Japan
⁹⁷ Astronomical Institute, Tohoku University, Sendai 980-8578, Japan
⁹⁸ Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 08826, Republic of Korea
⁹⁹ Leiden Observatory, Leiden University, Postbus 2300, 9513 RA Leiden, The Netherlands
¹⁰⁰ Physics Department, Brandeis University, 415 South Street, Waltham, MA 02453, USA
¹⁰¹ Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
¹⁰² School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
¹⁰³ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
¹⁰⁴ School of Astronomy and Space Sciences, University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, PR China
¹⁰⁵ Astronomy Department, University of Science and Technology of China, Hefei 230026, PR China
¹⁰⁶ Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
¹⁰⁷ University of Vermont, Burlington, VT 05405, USA
¹⁰⁸ National Radio Astronomy Observatory, NRAO Technology Center, 1180 Boxwood Estate Road, Charlottesville, VA 22903, USA
¹⁰⁹ Department of Physics, Villanova University, 800 E. Lancaster Ave, Villanova, PA 19085, USA
¹¹⁰ Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
¹¹¹ Fermi National Accelerator Laboratory, PO Box 500, Batavia, IL 60510, USA
¹¹² Instituto Nacional de Astrofísica, Óptica y Electrónica, Luis Enrique Erro 1, Tonantzintla, Puebla 72840, Mexico
¹¹³ Consejo Nacional de Ciencia y Tecnología, Av. Insurgentes Sur 1582, Col. Crédito Constructor, CDMX 03940, Mexico
¹¹⁴ National Chung-Shan Institute of Science and Technology, No.566, Ln. 134, Longyuan Rd., Longtan Dist. Taoyuan City 325, Taiwan, R.O.C.
¹¹⁵ Deptartment of Astronomy, University of California Berkeley, 501 Campbell, Berkeley, CA 94720, USA
¹¹⁶ Physikalisches Institut der Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
¹¹⁷ CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309, USA
¹¹⁸ Western University, 1151 Richmond Street, London, Ontario N6A 3K7, Canada
¹¹⁹ University of Massachusetts Boston, 100 William T, Morrissey Blvd, Boston, MA 02125, USA
¹²⁰ Research and Development Weather and Climate Models, Royal Netherlands Meteorological Institute, Utrechtseweg 297, 3731 GA De Bilt, The Netherlands
¹²¹ Department of Physics, McGill University, 3600 University Street, Montréal, QC H3A 2T8, Canada
¹²² McGill Space Institute, McGill University, 3550 University Street, Montréal, QC H3A 2A7, Canada
¹²³ CIFAR Azrieli Global Scholar, Gravity & the Extreme Universe Program, Canadian Institute for Advanced Research, 661 University Avenue, Suite 505, Toronto, ON M5G 1M1, Canada
¹²⁴ Department of Astrophysical and Planetary Sciences and Department of Physics, University of Colorado, Boulder, CO 80309, USA
¹²⁵ Department of Physical Science, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Nakaku, Sakai 599-8531, Osaka, Japan
¹²⁶ High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA
¹²⁷ European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago de Chile, Chile
¹²⁸ Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Magrans 08193, Barcelona, Spain
¹²⁹ ASIAA Hilo Office, 645 N. A‘ohoku Place, University Park, Hilo, HI 96720, USA
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¹³⁸ Physics Dept., CB 1105, Washington University, One Brookings Drive, St. Louis, MO 63130-4899, USA
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¹⁴⁵ Dept. of Physics and Astronomy, UCLA, Los Angeles, CA 90095, USA
¹⁴⁶ Owens Valley Radio Observatory, California Institute of Technology, Big Pine, CA 93513, USA
¹⁴⁷ Dept. of Astronomy, Radio Astronomy Laboratory, Univ. of California Berkeley, 601 Campbell, Berkeley, CA 94720, USA
¹⁴⁸ Universidad de las Américas Puebla, Sta. Catarina Mártir S/N, San Andrés Cholula, Puebla 72810, Mexico

Received: 13 January 2020
Accepted: 3 March 2020

Abstract

3C 279 is an archetypal blazar with a prominent radio jet that show broadband flux density variability across the entire electromagnetic spectrum. We use an ultra-high angular resolution technique – global Very Long Baseline Interferometry (VLBI) at 1.3 mm (230 GHz) – to resolve the innermost jet of 3C 279 in order to study its fine-scale morphology close to the jet base where highly variable γ-ray emission is thought to originate, according to various models. The source was observed during four days in April 2017 with the Event Horizon Telescope at 230 GHz, including the phased Atacama Large Millimeter/submillimeter Array (ALMA), at an angular resolution of ∼20 μas (at a redshift of z = 0.536 this corresponds to ∼0.13 pc  ∼ 1700 Schwarzschild radii with a black hole mass M_BH = 8 × 10⁸ M_⊙). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation. We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across different imaging methods and model-fitting techniques, and therefore appears robust. Owing to its compactness and brightness, we associate the northern nuclear structure as the VLBI “core”. This morphology can be interpreted as either a broad resolved jet base or a spatially bent jet. We also find significant day-to-day variations in the closure phases, which appear most pronounced on the triangles with the longest baselines. Our analysis shows that this variation is related to a systematic change of the source structure. Two inner jet components move non-radially at apparent speeds of ∼15 c and ∼20 c (∼1.3 and ∼1.7 μas day⁻¹, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3 mm core and the outer jet. The intrinsic brightness temperature of the jet components are ≲10¹⁰ K, a magnitude or more lower than typical values seen at ≥7 mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C 279 becomes optically thin at short (mm) wavelengths.