CaltechAUTHORS
Published March 20, 2021 | Version Published
Journal Article Open

First M87 Event Horizon Telescope Results. VII. Polarization of the Ring

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Abstract

In 2017 April, the Event Horizon Telescope (EHT) observed the near-horizon region around the supermassive black hole at the core of the M87 galaxy. These 1.3 mm wavelength observations revealed a compact asymmetric ring-like source morphology. This structure originates from synchrotron emission produced by relativistic plasma located in the immediate vicinity of the black hole. Here we present the corresponding linear-polarimetric EHT images of the center of M87. We find that only a part of the ring is significantly polarized. The resolved fractional linear polarization has a maximum located in the southwest part of the ring, where it rises to the level of ~15%. The polarization position angles are arranged in a nearly azimuthal pattern. We perform quantitative measurements of relevant polarimetric properties of the compact emission and find evidence for the temporal evolution of the polarized source structure over one week of EHT observations. The details of the polarimetric data reduction and calibration methodology are provided. We carry out the data analysis using multiple independent imaging and modeling techniques, each of which is validated against a suite of synthetic data sets. The gross polarimetric structure and its apparent evolution with time are insensitive to the method used to reconstruct the image. These polarimetric images carry information about the structure of the magnetic fields responsible for the synchrotron emission. Their physical interpretation is discussed in an accompanying publication.

Additional Information

© 2021. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2020 November 23; revised 2021 February 15; accepted 2021 February 16; published 2021 March 24. The authors of the present Letter are extremely grateful to the anonymous referee for the thorough review and highly appreciate all comments and suggestions that significantly improved the quality of the manuscript. The authors of the present Letter thank the following organizations and programs: the Academy of Finland (projects 274477, 284495, 312496, 315721); the Alexander von Humboldt Stiftung; Agencia Nacional de Investigación y Desarrollo (ANID), Chile via NCN19_058 (TITANs), and Fondecyt 3190878; an Alfred P. Sloan Research Fellowship; Allegro, the European ALMA Regional Centre node in the Netherlands, the NL astronomy research network NOVA and the astronomy institutes of the University of Amsterdam, Leiden University and Radboud University; the black hole Initiative at Harvard University, through a grant (60477) from the John Templeton Foundation; the China Scholarship Council; Consejo Nacional de Ciencia y Tecnología (CONACYT, Mexico, projects U0004-246083, U0004-259839, F0003-272050, M0037-279006, F0003-281692, 104497, 275201, 263356); the Delaney Family via the Delaney Family John A. Wheeler Chair at Perimeter Institute; Dirección General de Asuntos del Personal Académico-Universidad Nacional Autónoma de México (DGAPA-UNAM, projects IN112417 and IN112820); the EACOA Fellowship of the East Asia Core Observatories Association; the European Research Council Synergy Grant "BlackHoleCam: Imaging the Event Horizon of Black Holes" (grant 610058); the Generalitat Valenciana postdoctoral grant APOSTD/2018/177 and GenT Program (project CIDEGENT/2018/021); MICINN Research Project PID2019-108995GB-C22; the Gordon and Betty Moore Foundation (grants GBMF- 3561, GBMF-5278); the Istituto Nazionale di Fisica Nucleare (INFN) sezione di Napoli, iniziative specifiche TEONGRAV; the International Max Planck Research School for Astronomy and Astrophysics at the Universities of Bonn and Cologne; Joint Princeton/Flatiron and Joint Columbia/Flatiron Postdoctoral Fellowships, research at the Flatiron Institute is supported by the Simons Foundation; the Japanese Government (Monbukagakusho: MEXT) Scholarship; the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for JSPS Research Fellowship (JP17J08829); the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (CAS, grants QYZDJ-SSW-SLH057, QYZDJSSW- SYS008, ZDBS-LY-SLH011); the Leverhulme Trust Early Career Research Fellowship; the Max-Planck-Gesellschaft (MPG); the Max Planck Partner Group of the MPG and the CAS; the MEXT/JSPS KAKENHI (grants 18KK0090, JP18K13594, JP18K03656, JP18H03721, 18K03709, 18H01245, 25120007); the Malaysian Fundamental Research Grant Scheme (FRGS) FRGS/1/2019/STG02/UM/02/6; the MIT International Science and Technology Initiatives (MISTI) Funds; the Ministry of Science and Technology (MOST) of Taiwan (105-2112-M-001-025-MY3, 106-2112-M-001-011, 106-2119- M-001-027, 107-2119-M-001-017, 107-2119-M-001-020, 107-2119-M-110-005, 108-2112-M-001-048, and 109-2124-M-001-005); the National Aeronautics and Space Administration (NASA, Fermi Guest Investigator grant 80NSSC20K1567 and 80NSSC20K1567, NASA Astrophysics Theory Program grant 80NSSC20K0527, NASA NuSTAR award 80NSSC20K0645, NASA grant NNX17AL82G, and Hubble Fellowship grant HST-HF2-51431.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555); the National Institute of Natural Sciences (NINS) of Japan; the National Key Research and Development Program of China (grant 2016YFA0400704, 2016YFA0400702); the National Science Foundation (NSF, grants AST-0096454, AST-0352953, AST-0521233, AST-0705062, AST-0905844, AST-0922984, AST-1126433, AST-1140030, DGE-1144085, AST-1207704, AST-1207730, AST-1207752, MRI-1228509, OPP-1248097, AST-1310896, AST-1337663, AST-1440254, AST-1555365, AST-1615796, AST-1715061, AST-1716327, AST-1716536, OISE-1743747, AST-1816420, AST-1903847, AST-1935980, AST-2034306); the Natural Science Foundation of China (grants 11573051, 11633006, 11650110427, 10625314, 11721303, 11725312, 11933007, 11991052, 11991053); a fellowship of China Postdoctoral Science Foundation (2020M671266); the Natural Sciences and Engineering Research Council of Canada (NSERC, including a Discovery Grant and the NSERC Alexander Graham Bell Canada Graduate Scholarships-Doctoral Program); the National Research Foundation of Korea (the Global PhD Fellowship Grant: grants 2014H1A2A1018695, NRF-2015H1A2A1033752, 2015- R1D1A1A01056807, the Korea Research Fellowship Program: NRF-2015H1D3A1066561, Basic Research Support grant 2019R1F1A1059721); the Netherlands Organization for Scientific Research (NWO) VICI award (grant 639.043.513) and Spinoza Prize SPI 78-409; the New Scientific Frontiers with Precision Radio Interferometry Fellowship awarded by the South African Radio Astronomy Observatory (SARAO), which is a facility of the National Research Foundation (NRF), an agency of the Department of Science and Innovation (DSI) of South Africa; the South African Research Chairs Initiative of the Department of Science and Innovation and National Research Foundation; the Onsala Space Observatory (OSO) national infrastructure, for the provisioning of its facilities/observational support (OSO receives funding through the Swedish Research Council under grant 2017-00648) the Perimeter Institute for Theoretical Physics (research at Perimeter Institute is supported by the Government of Canada through the Department of Innovation, Science and Economic Development and by the Province of Ontario through the Ministry of Research, Innovation and Science); the Spanish Ministerio de Ciencia e Innovación (grants PGC2018-098915-B-C21, AYA2016-80889-P; PID2019-108995GB-C21, PGC2018-098915-B-C21); the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709); the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709); the Toray Science Foundation; the Consejería de Economía, Conocimiento, Empresas y Universidad of the Junta de Andalucía (grant P18-FR-1769), the Consejo Superior de Investigaciones Científicas (grant 2019AEP112); the US Department of Energy (USDOE) through the Los Alamos National Laboratory (operated by Triad National Security, LLC, for the National Nuclear Security Administration of the USDOE (Contract 89233218CNA000001); the European Union's Horizon 2020 research and innovation program under grant agreement No 730562 RadioNet; ALMA North America Development Fund; the Academia Sinica; Chandra TM6-17006X; Chandra award DD7-18089X. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), supported by NSF grant ACI-1548562, and CyVerse, supported by NSF grants DBI-0735191, DBI-1265383, and DBI-1743442. XSEDE Stampede2 resource at TACC was allocated through TG-AST170024 and TG-AST080026N. XSEDE JetStream resource at PTI and TACC was allocated through AST170028. The simulations were performed in part on the SuperMUC cluster at the LRZ in Garching, on the LOEWE cluster in CSC in Frankfurt, and on the HazelHen cluster at the HLRS in Stuttgart. This research was enabled in part by support provided by Compute Ontario (http://computeontario.ca), Calcul Quebec (http://www.calculquebec.ca) and Compute Canada (http://www.computecanada.ca). We thank the staff at the participating observatories, correlation centers, and institutions for their enthusiastic support. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2016.1.01154.V. ALMA is a partnership of the European Southern Observatory (ESO; Europe, representing its member states), NSF, and National Institutes of Natural Sciences of Japan, together with National Research Council (Canada), Ministry of Science and Technology (MOST; Taiwan), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA; Taiwan), and Korea Astronomy and Space Science Institute (KASI; Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, Associated Universities, Inc. (AUI)/NRAO, and the National Astronomical Observatory of Japan (NAOJ). The NRAO is a facility of the NSF operated under cooperative agreement by AUI. This paper has made use of the following APEX data: Project ID T-091.F-0006-2013. APEX is a collaboration between the Max-Planck-Institut für Radioastronomie (Germany), ESO, and the Onsala Space Observatory (Sweden). The SMA is a joint project between the SAO and ASIAA and is funded by the Smithsonian Institution and the Academia Sinica. The JCMT is operated by the East Asian Observatory on behalf of the NAOJ, ASIAA, and KASI, as well as the Ministry of Finance of China, Chinese Academy of Sciences, and the National Key R&D Program (No. 2017YFA0402700) of China. Additional funding support for the JCMT is provided by the Science and Technologies Facility Council (UK) and participating universities in the UK and Canada. The LMT is a project operated by the Instituto Nacional de Astrofísica, Óptica, y Electrónica (Mexico) and the University of Massachusetts at Amherst (USA), with financial support from the Consejo Nacional de Ciencia y Tecnología and the National Science Foundation. The IRAM 30-m telescope on Pico Veleta, Spain is operated by IRAM and supported by CNRS (Centre National de la Recherche Scientifique, France), MPG (Max-Planck- Gesellschaft, Germany) and IGN (Instituto Geográfico Nacional, Spain). The SMT is operated by the Arizona Radio Observatory, a part of the Steward Observatory of the University of Arizona, with financial support of operations from the State of Arizona and financial support for instrumentation development from the NSF. The SPT is supported by the National Science Foundation through grant PLR- 1248097. Partial support is also provided by the NSF Physics Frontier Center grant PHY-1125897 to the Kavli Institute of Cosmological Physics at the University of Chicago, the Kavli Foundation and the Gordon and Betty Moore Foundation grant GBMF 947. The SPT hydrogen maser was provided on loan from the GLT, courtesy of ASIAA. The EHTC has received generous donations of FPGA chips from Xilinx Inc., under the Xilinx University Program. The EHTC has benefited from technology shared under open-source license by the Collaboration for Astronomy Signal Processing and Electronics Research (CASPER). The EHT project is grateful to T4Science and Microsemi for their assistance with Hydrogen Masers. This research has made use of NASA's Astrophysics Data System. We gratefully acknowledge the support provided by the extended staff of the ALMA, both from the inception of the ALMA Phasing Project through the observational campaigns of 2017 and 2018. We would like to thank A. Deller and W. Brisken for EHT-specific support with the use of DiFX. We acknowledge the significance that Maunakea, where the SMA and JCMT EHT stations are located, has for the indigenous Hawaiian people. Facilities: EHT - , ALMA - , APEX - Atacama Pathfinder Experiment, IRAM:30 m - , JCMT - James Clerk Maxwell Telescope, LMT - , SMA - SubMillimeter Array, ARO:SMT - , SPT - South Pole Telescope. Software: AIPS (Greisen 2003), ParselTongue (Kettenis et al. 2006), GNU Parallel (Tange 2011), eht-imaging (Chael et al. 2016), Difmap (Shepherd 2011), Numpy (van der Walt et al. 2011), Scipy (Jones et al. 2001), Pandas (McKinney 2010), Astropy (The Astropy Collaboration et al. 2013, 2018), Jupyter (Kluyver et al. 2016), Matplotlib (Hunter 2007), Themis (Broderick et al. 2020a), DMC (Pesce 2021), polsolve (Martí-Vidal et al. 2021), GPCAL (Park et al. 2021).

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Additional details

Identifiers

Eprint ID
108545
Resolver ID
CaltechAUTHORS:20210324-134820707

Funding

Academy of Finland
274477
Academy of Finland
284495
Academy of Finland
312496
Academy of Finland
315721
Alexander von Humboldt Stiftung
Agencia Nacional de Investigación y Desarrollo (ANID)
NCN19_058
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)
3190878
Alfred P. Sloan Foundation
Allegro
ALMA Regional Centre
Nederlandse Onderzoekschool Voor Astronomie (NOVA)
University of Amsterdam
Leiden University
Radboud University
Harvard University
John Templeton Foundation
60477
China Scholarship Council
Consejo Nacional de Ciencia y Tecnología (CONACYT)
U0004-246083
Consejo Nacional de Ciencia y Tecnología (CONACYT)
U0004-259839
Consejo Nacional de Ciencia y Tecnología (CONACYT)
F0003-272050
Consejo Nacional de Ciencia y Tecnología (CONACYT)
M0037-279006
Consejo Nacional de Ciencia y Tecnología (CONACYT)
F0003-281692
Consejo Nacional de Ciencia y Tecnología (CONACYT)
104497
Consejo Nacional de Ciencia y Tecnología (CONACYT)
275201
Consejo Nacional de Ciencia y Tecnología (CONACYT)
263356
Delaney Family John A. Wheeler Chair
Dirección General de Asuntos del Personal Académico-Universidad Nacional Autónoma de México
IN112417
Dirección General de Asuntos del Personal Académico-Universidad Nacional Autónoma de México
IN112820
East Asia Core Observatories Association
European Research Council (ERC)
610058
Generalitat Valenciana
APOSTD/2018/177
Generalitat Valenciana
CIDEGENT/2018/021
Ministerio de Ciencia e Innovación (MCINN)
PID2019-108995GB-C22
Gordon and Betty Moore Foundation
GBMF-3561
Gordon and Betty Moore Foundation
GBMF-5278
Istituto Nazionale di Fisica Nucleare (INFN)
International Max Planck Research School (IMPRS) for Astronomy and Astrophysics
Princeton University
Flatiron Institute
Columbia University
Simons Foundation
Monbukagakusho
Ministry of Education, Culture, Sports, Science and Technology (MEXT)
Japan Society for the Promotion of Science (JSPS)
JP17J08829
Key Research Program of Frontier Sciences
Chinese Academy of Sciences
QYZDJ-SSW-SLH057
Chinese Academy of Sciences
QYZDJSSW-SYS008
Chinese Academy of Sciences
ZDBS-LY-SLH011
Leverhulme Trust
Max-Planck-Gesellschaft (MPG)
Japan Society for the Promotion of Science (JSPS)
18KK0090
Japan Society for the Promotion of Science (JSPS)
JP18K13594
Japan Society for the Promotion of Science (JSPS)
JP18K03656
Japan Society for the Promotion of Science (JSPS)
JP18H03721
Japan Society for the Promotion of Science (JSPS)
18K03709
Japan Society for the Promotion of Science (JSPS)
18H01245
Japan Society for the Promotion of Science (JSPS)
25120007
Malaysian Fundamental Research Grant
FRGS/1/2019/STG02/UM/02/6
Massachusetts Institute of Technology (MIT)
Ministry of Science and Technology (Taipei)
105-2112-M-001-025-MY3
Ministry of Science and Technology (Taipei)
106-2112-M-001-011
Ministry of Science and Technology (Taipei)
106-2119-M-001-027
Ministry of Science and Technology (Taipei)
107-2119-M-001-017
Ministry of Science and Technology (Taipei)
107-2119-M-001-020
Ministry of Science and Technology (Taipei)
107-2119-M-110-005
Ministry of Science and Technology (Taipei)
108-2112-M-001-048
Ministry of Science and Technology (Taipei)
109-2124-M-001-005
NASA
80NSSC20K1567
NASA
80NSSC20K0527
NASA
80NSSC20K0645
NASA
NNX17AL82G
NASA Hubble Fellowship
HST-HF2-51431.001-A
NASA
NAS5-26555
National Institute of Natural Sciences (NINS)
National Key Research and Development Program of China
2016YFA0400704
National Key Research and Development Program of China
2016YFA0400702
NSF
AST-0096454
NSF
AST-0352953
NSF
AST-0521233
NSF
AST-0705062
NSF
AST-0905844
NSF
AST-0922984
NSF
AST-1126433
NSF
AST-1140030
NSF Graduate Research Fellowship
DGE-1144085
NSF
AST-1207704
NSF
AST-1207730
NSF
AST-1207752
NSF
MRI-1228509
NSF
OPP-1248097
NSF
AST-1310896
NSF
AST-1337663
NSF
AST-1440254
NSF
AST-1555365
NSF
AST-1615796
NSF
AST-1715061
NSF
AST-1716327
NSF
AST-1716536
NSF
OISE-1743747
NSF
AST-1816420
NSF
AST-1903847
NSF
AST-1935980
NSF
AST-2034306
National Natural Science Foundation of China
11573051
National Natural Science Foundation of China
11633006
National Natural Science Foundation of China
11650110427
National Natural Science Foundation of China
10625314
National Natural Science Foundation of China
11721303
National Natural Science Foundation of China
11725312
National Natural Science Foundation of China
11933007
National Natural Science Foundation of China
11991052
National Natural Science Foundation of China
11991053
China Postdoctoral Science Foundation
2020M671266
Natural Sciences and Engineering Research Council of Canada (NSERC)
National Research Foundation of Korea
2014H1A2A1018695
National Research Foundation of Korea
2015H1A2A1033752
National Research Foundation of Korea
2015-R1D1A1A01056807
National Research Foundation of Korea
NRF-2015H1D3A1066561
National Research Foundation of Korea
2019R1F1A1059721
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)
639.043.513
Spinoza Prize
SPI 78-409
South African Radio Astronomy Observatory (SARAO)
National Research Foundation (South Africa)
Department of Science and Innovation (South Africa)
Onsala Space Observatory (OSO)
Swedish Research Council
2017-00648
Perimeter Institute for Theoretical Physics
Department of Innovation, Science and Economic Development (Canada)
Province of Ontario Ministry of Research, Innovation and Science
Severo Ochoa
PGC2018-098915-B-C21
Ministerio de Economía y Competitividad (MINECO)
AYA2016-80889-P
Ministerio de Economía, Industria y Competitividad (MINECO)
PID2019-108995GB-C21
Severo Ochoa
PGC2018-098915-B-C21
Ministerio de Ciencia, Innovación y Universidades (MCIU)
Severo Ochoa
SEV-2017-0709
Toray Science Foundation
Junta de Andalucía
P18-FR-1769
Consejo Superior de Investigaciones Científicas
2019AEP112
Department of Energy (DOE)
89233218CNA000001
European Research Council (ERC)
730562 RadioNet
ALMA North America Development Fund
Academia Sinica
NASA Chandra
TM6-17006X
NASA Chandra
DD7-18089X
NSF
ACI-1548562
NSF
DBI-0735191
NSF
DBI-1265383
NSF
DBI-1743442
NSF
TG-AST170024
NSF
TG-AST080026N
NSF
AST-170028
Compute Ontario
Calcul Quebec
Compute Canada
Smithsonian Institution
Academia Sinica
National Key Research and Development Program of China
2017YFA0402700
Science and Technologies Facilities Council (STFC)
State of Arizona
NSF
PLR-1248097
NSF
PHY-1125897
Kavli Foundation
Gordon and Betty Moore Foundation
GBMF 947

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2021-03-24
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Updated
2021-11-16
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