First polarization study of the M87 jet and active galactic nuclei at submillimeter wavelengths with ALMA

¹ Dipartimento di Fisica, Università degli Studi di Cagliari, SP Monserrato-Sestu km 0.7, I-09042 Monserrato (CA), Italy
² Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, R. do Matão, 1226, São Paulo, SP 05508-090, Brazil
³ INAF – Osservatorio Astronomico di Cagliari, via della Scienza 5, I-09047 Selargius (CA), Italy
⁴ Massachusetts Institute of Technology Haystack Observatory, 99 Millstone Road, Westford, MA 01886, USA
⁵ Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura 763-0355, Santiago de Chile, Chile
⁶ INAF-Istituto di Radioastronomia, Via P. Gobetti 101, I-40129 Bologna, Italy
⁷ Departament d’Astronomia i Astrofísica, Universitat de València, C. Dr. Moliner 50, E-46100 Burjassot, València, Spain
⁸ Observatori Astronòmic, Universitat de València, C. Catedrático José Beltrán 2, E-46980 Paterna, València, Spain
⁹ Dipartimento di Fisica “E. Pancini”, Università di Napoli “Federico II”, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126 Napoli, Italy
¹⁰ INFN Sez. di Napoli, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126 Napoli, Italy
¹¹ INAF-Istituto di Radioastronomia & Italian ALMA Regional Centre, Via P. Gobetti 101, I-40129 Bologna, Italy
¹² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
¹³ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁴ Black Hole Initiative at Harvard University, 20 Garden Street, Cambridge, MA 02138, USA
¹⁵ Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, E-18008 Granada, Spain
¹⁶ Department of Physics, Faculty of Science, Universiti Malaya, 50603 Kuala Lumpur, Malaysia
¹⁷ Department of Physics & Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA
¹⁸ Physics & Astronomy Department, Rice University, Houston, TX 77005-1827, USA
¹⁹ Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
²⁰ Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, AS/NTU No. 1, Sec. 4, Roosevelt Rd., Taipei 106216, Taiwan, ROC
²¹ Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, SE-43992 Onsala, Sweden
²² Steward Observatory and Department of Astronomy, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA
²³ Yale Center for Astronomy & Astrophysics, Yale University, 52 Hillhouse Avenue, New Haven, CT 06511, USA
²⁴ Astronomy Department, Universidad de Concepción, Casilla 160-C, Concepción, Chile
²⁵ Department of Physics, University of Illinois, 1110 West Green Street, Urbana, IL 61801, USA
²⁶ Fermi National Accelerator Laboratory, MS209, P.O. Box 500, Batavia, IL 60510, USA
²⁷ Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
²⁸ East Asian Observatory, 660 N. A’ohoku Place, Hilo, HI 96720, USA
²⁹ James Clerk Maxwell Telescope (JCMT), 660 N. A’ohoku Place, Hilo, HI 96720, USA
³⁰ California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA
³¹ Institute of Astronomy and Astrophysics, Academia Sinica, 645 N. A’ohoku Place, Hilo, HI 96720, USA
³² Department of Physics and Astronomy, University of Hawaii at Manoa, 2505 Correa Road, Honolulu, HI 96822, USA
³³ Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, F-38406 Saint Martin d’Hères, France
³⁴ Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, ON N2L 2Y5, Canada
³⁵ Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
³⁶ Waterloo Centre for Astrophysics, University of Waterloo, Waterloo, ON N2L 3G1, Canada
³⁷ Department of Astrophysics, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands
³⁸ Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
³⁹ Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
⁴⁰ Department of Physics, University of Chicago, 5720 South Ellis Avenue, Chicago, IL 60637, USA
⁴¹ Enrico Fermi Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
⁴² Princeton Gravity Initiative, Jadwin Hall, Princeton University, Princeton, NJ 08544, USA
⁴³ Data Science Institute, University of Arizona, 1230 N. Cherry Ave., Tucson, AZ 85721, USA
⁴⁴ Program in Applied Mathematics, University of Arizona, 617 N. Santa Rita, Tucson, AZ 85721, USA
⁴⁵ Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, NY 14853, USA
⁴⁶ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, PR China
⁴⁷ Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100101, PR China
⁴⁸ Korea Astronomy and Space Science Institute, Daedeok-daero 776, Yuseong-gu, Daejeon 34055, Republic of Korea
⁴⁹ Department of Astronomy, Yonsei University, Yonsei-ro 50, Seodaemun-gu, 03722 Seoul, Republic of Korea
⁵⁰ WattTime, 490 43rd Street, Unit 221, Oakland, CA 94609, USA
⁵¹ Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801, USA
⁵² Instituto de Astronomía, Universidad Nacional Autònoma de México (UNAM), Apdo Postal 70-264, Ciudad de México, Mexico
⁵³ Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, D-60438 Frankfurt am Main, Germany
⁵⁴ Research Center for Astronomical Computing, Zhejiang Laboratory, Hangzhou 311100, PR China
⁵⁵ Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shengrong Road 520, Shanghai 201210, PR China
⁵⁶ Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544, USA
⁵⁷ Wits Centre for Astrophysics, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein, Johannesburg 2050, South Africa
⁵⁸ Department of Physics, University of Pretoria, Hatfield, Pretoria 0028, South Africa
⁵⁹ Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University, Makhanda 6140, South Africa
⁶⁰ ASTRON, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
⁶¹ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, F-92195 Meudon, France
⁶² JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309, USA
⁶³ National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100101, PR China
⁶⁴ Las Cumbres Observatory, 6740 Cortona Drive, Suite 102, Goleta, CA 93117-5575, USA
⁶⁵ Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
⁶⁶ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
⁶⁷ Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 32-D476, 77 Massachusetts Ave., Cambridge, MA 02142, USA
⁶⁸ Google Research, 355 Main St., Cambridge, MA 02142, USA
⁶⁹ Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Emil-Fischer-Str. 31, D-97074 Würzburg, Germany
⁷⁰ Department of History of Science, Harvard University, Cambridge, MA 02138, USA
⁷¹ Department of Physics, Harvard University, Cambridge, MA 02138, USA
⁷² NCSA, University of Illinois, 1205 W. Clark St., Urbana, IL 61801, USA
⁷³ Institute for Mathematics and Interdisciplinary Center for Scientific Computing, Heidelberg University, Im Neuenheimer Feld 205, Heidelberg 69120, Germany
⁷⁴ Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg, Germany
⁷⁵ CP3-Origins, University of Southern Denmark, Campusvej 55, DK-5230 Odense, Denmark
⁷⁶ Instituto Nacional de Astrofísica, Óptica y Electr’ønica. Apartado Postal 51 y 216, 72000. Puebla Pue., Mexico
⁷⁷ Consejo Nacional de Humanidades, Ciencia y Tecnología, Av. Insurgentes Sur 1582, 03940, Ciudad de México, Mexico
⁷⁸ Key Laboratory for Research in Galaxies and Cosmology, Chinese Academy of Sciences, Shanghai 200030, PR China
⁷⁹ Graduate School of Science, Nagoya City University, Yamanohata 1, Mizuho-cho, Mizuho-ku, Nagoya 467-8501, Aichi, Japan
⁸⁰ Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan
⁸¹ Department of Physics, McGill University, 3600 rue University, Montréal, QC H3A 2T8, Canada
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 Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
⁸⁷ Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
⁸⁸ The Institute of Statistical Mathematics, 10-3 Midori-cho, Tachikawa, Tokyo 190-8562, Japan
⁸⁹ Department of Statistical Science, The Graduate University for Advanced Studies (SOKENDAI), 10-3 Midori-cho, Tachikawa, Tokyo 190-8562, Japan
⁹⁰ Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8583, Japan
⁹¹ Leiden Observatory, Leiden University, Postbus 2300, 9513 RA Leiden, The Netherlands
⁹² ASTRAVEO LLC, PO Box 1668, Gloucester, MA 01931, USA
⁹³ Applied Materials Inc., 35 Dory Road, Gloucester, MA 01930, USA
⁹⁴ Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave., Boston, MA 02215, USA
⁹⁵ University of Science and Technology, Gajeong-ro 217, Yuseong-gu, Daejeon 34113, Republic of Korea
⁹⁶ Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582, Japan
⁹⁷ Joint Institute for VLBI ERIC (JIVE), Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
⁹⁸ CSIRO, Space and Astronomy, PO Box 76, Epping, NSW 1710, Australia
⁹⁹ Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
¹⁰⁰ Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
¹⁰¹ Kogakuin University of Technology & Engineering, Academic Support Center, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan
¹⁰² Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata 950-2181, Japan
¹⁰³ Physics Department, National Sun Yat-Sen University, No. 70, Lien-Hai Road, Kaosiung City 80424, Taiwan, ROC
¹⁰⁴ School of Astronomy and Space Science, Nanjing University, Nanjing 210023, PR China
¹⁰⁵ Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University, Nanjing 210023, PR China
¹⁰⁶ Common Crawl Foundation, 9663 Santa Monica Blvd. 425, Beverly Hills, CA 90210 USA
¹⁰⁷ Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso, Chile
¹⁰⁸ Department of Physics, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106216, Taiwan, ROC
¹⁰⁹ Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de Mexico, Morelia 58089, Mexico
¹¹⁰ David Rockefeller Center for Latin American Studies, Harvard University, 1730 Cambridge Street, Cambridge, MA 02138, USA
¹¹¹ Yunnan Observatories, Chinese Academy of Sciences, 650011 Kunming, Yunnan Province, PR China
¹¹² Center for Astronomical Mega-Science, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, PR China
¹¹³ Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, 650011 Kunming, PR China
¹¹⁴ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
¹¹⁵ Gravitation and Astroparticle Physics Amsterdam (GRAPPA) Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
¹¹⁶ School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China
¹¹⁷ Institut de Radioastronomie Millimétrique (IRAM), Avenida Divina Pastora 7, Local 20, E-18012 Granada, Spain
¹¹⁸ National Institute of Technology, Hachinohe College, 16-1 Uwanotai, Tamonoki, Hachinohe City, Aomori 039-1192, Japan
¹¹⁹ Research Center for Astronomy, Academy of Athens, Soranou Efessiou 4, 115 27 Athens, Greece
¹²⁰ Department of Physics, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085, USA
¹²¹ Physics Department, Washington University, CB 1105, St. Louis, MO 63130, USA
¹²² Departamento de Matemática da Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA), Campus de Santiago, 3810-193 Aveiro, Portugal
¹²³ School of Physics, Georgia Institute of Technology, 837 State St NW, Atlanta, GA 30332, USA
¹²⁴ School of Space Research, Kyung Hee University, 1732, Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104, Republic of Korea
¹²⁵ Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada
¹²⁶ Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada
¹²⁷ Canadian Institute for Advanced Research, 180 Dundas St West, Toronto, ON M5G 1Z8, Canada
¹²⁸ Dipartimento di Fisica, Università di Trieste, I-34127 Trieste, Italy
¹²⁹ INFN Sez. di Trieste, I-34127 Trieste, Italy
¹³⁰ Department of Physics, National Taiwan Normal University, No. 88, Sec. 4, Tingzhou Rd., Taipei 116, Taiwan, ROC
¹³¹ Center of Astronomy and Gravitation, National Taiwan Normal University, No. 88, Sec. 4, Tingzhou Road, Taipei 116, Taiwan, ROC
¹³² Finnish Centre for Astronomy with ESO, University of Turku, FI-20014 Turun Yliopisto, Finland
¹³³ Aalto University Metsähovi Radio Observatory, Metsähovintie 114, FI-02540 Kylmälä, Finland
¹³⁴ Gemini Observatory/NSF NOIRLab, 670 N. A’ohōkū Place, Hilo, HI 96720, USA
¹³⁵ Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, D-60438 Frankfurt, Germany
¹³⁶ School of Mathematics, Trinity College, Dublin 2, Ireland
¹³⁷ Department of Physics, University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7, Canada
¹³⁸ Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
¹³⁹ Hiroshima Astrophysical Science Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
¹⁴⁰ Aalto University Department of Electronics and Nanoengineering, PL 15500, FI-00076 Aalto, Finland
¹⁴¹ Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
¹⁴² National Biomedical Imaging Center, Peking University, Beijing 100871, PR China
¹⁴³ College of Future Technology, Peking University, Beijing 100871, PR China
¹⁴⁴ Tokyo Electron Technology Solutions Limited, 52 Matsunagane, Iwayado, Esashi, Oshu, Iwate 023-1101, Japan
¹⁴⁵ Department of Physics and Astronomy, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada
¹⁴⁶ Netherlands Organisation for Scientific Research (NWO), Postbus 93138, 2509 AC Den Haag, The Netherlands
¹⁴⁷ Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578, Japan
¹⁴⁸ Astronomical Institute, Tohoku University, Sendai 980-8578, Japan
¹⁴⁹ Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 08826, Republic of Korea
¹⁵⁰ University of New Mexico, Department of Physics and Astronomy, Albuquerque, NM 87131, USA
¹⁵¹ Physics Department, Brandeis University, 415 South Street, Waltham, MA 02453, USA
¹⁵² Tuorla Observatory, Department of Physics and Astronomy, University of Turku, FI-20014 Turun Yliopisto, Finland
¹⁵³ Radboud Excellence Fellow of Radboud University, Nijmegen, The Netherlands
¹⁵⁴ School of Natural Sciences, Institute for Advanced Study, 1 Einstein Drive, Princeton, NJ 08540, USA
¹⁵⁵ School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China
¹⁵⁶ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
¹⁵⁷ Center for Astronomy and Astrophysics and Department of Physics, Fudan University, Shanghai 200438, PR China
¹⁵⁸ Astronomy Department, University of Science and Technology of China, Hefei 230026, PR China
¹⁵⁹ Department of Physics and Astronomy, Michigan State University, 567 Wilson Rd, East Lansing, MI 48824, USA

^⋆ Corresponding author.

Received: 14 February 2025
Accepted: 4 April 2025

Abstract

Aims. We investigated the polarization and Faraday properties of Messier 87 (M87) and seven other radio-loud active galactic nuclei (AGNs) at λ0.87 mm (345 GHz) using the Atacama Large Millimeter/submillimeter Array (ALMA). Our goal was to characterize the linear polarization (LP) fractions, measure Faraday rotation measures (RMs), and examine the magnetic field structures in the emission regions of these AGNs.

Methods. We conducted full-polarization observations as part of the ALMA Band 7 very long baseline interferometry (VLBI) commissioning during the April 2021 Event Horizon Telescope (EHT) campaign. We analyzed the LP fractions and RMs to assess the nature of Faraday screens and magnetic fields in the submillimeter emission regions.

Results. We find LP fractions between 1% and 17% and RMs exceeding 10⁵ rad m⁻², which are 1–2 orders of magnitude higher than typically observed at longer wavelengths (λ>3 mm). This suggests denser Faraday screens or stronger magnetic fields. Additionally, we present the first submillimeter polarized images of the M87 jet and the observed AGNs, revealing RM gradients and sign reversals in the M87 jet indicative of a kiloparsec-scale helical magnetic field structure.

Conclusions. Our results provide essential constraints for calibrating, analyzing, and interpreting VLBI data from the EHT at 345 GHz, representing a critical step toward submillimeter VLBI imaging.