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First M87 Event Horizon Telescope Results. III. Data Processing and Calibration

Akiyama, Kazunori and Bouman, Katherine L. (2019) First M87 Event Horizon Telescope Results. III. Data Processing and Calibration. Astrophysical Journal Letters, 875 (1). Art. No. L3. ISSN 2041-8213. https://resolver.caltech.edu/CaltechAUTHORS:20190410-102159947

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Abstract

We present the calibration and reduction of Event Horizon Telescope (EHT) 1.3 mm radio wavelength observations of the supermassive black hole candidate at the center of the radio galaxy M87 and the quasar 3C 279, taken during the 2017 April 5–11 observing campaign. These global very long baseline interferometric observations include for the first time the highly sensitive Atacama Large Millimeter/submillimeter Array (ALMA); reaching an angular resolution of 25 μas, with characteristic sensitivity limits of ~1 mJy on baselines to ALMA and ~10 mJy on other baselines. The observations present challenges for existing data processing tools, arising from the rapid atmospheric phase fluctuations, wide recording bandwidth, and highly heterogeneous array. In response, we developed three independent pipelines for phase calibration and fringe detection, each tailored to the specific needs of the EHT. The final data products include calibrated total intensity amplitude and phase information. They are validated through a series of quality assurance tests that show consistency across pipelines and set limits on baseline systematic errors of 2% in amplitude and 1° in phase. The M87 data reveal the presence of two nulls in correlated flux density at ~3.4 and ~8.3 Gλ and temporal evolution in closure quantities, indicating intrinsic variability of compact structure on a timescale of days, or several light-crossing times for a few billion solar-mass black hole. These measurements provide the first opportunity to image horizon-scale structure in M87.


Item Type:Article
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https://doi.org/10.3847/2041-8213/ab0c57DOIArticle
ORCID:
AuthorORCID
Akiyama, Kazunori0000-0002-9475-4254
Bouman, Katherine L.0000-0003-0077-4367
Additional Information:© 2019 The American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 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 2019 February 11; revised 2019 March 3; accepted 2019 March 3; published 2019 April 10. The authors of this Letter thank the following organizations and programs: the Academy of Finland (projects 274477, 284495, 312496); the Advanced European Network of E-infrastructures for Astronomy with the SKA (AENEAS) project, supported by the European Commission Framework Programme Horizon 2020 Research and Innovation action under grant agreement 731016; the Alexander von Humboldt Stiftung; the Black Hole Initiative at Harvard University, through a grant (60477) from the John Templeton Foundation; the China Scholarship Council; Comisión Nacional de Investigación Científica y Tecnológica (CONICYT, Chile, via PIA ACT172033, Fondecyt 1171506, BASAL AFB-170002, ALMA-conicyt 31140007); Consejo Nacional de Ciencia y Tecnología (CONACYT, Mexico, projects 104497, 275201, 279006, 281692); 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, project IN112417); the European Research Council Synergy Grant "BlackHoleCam: Imaging the Event Horizon of Black Holes" (grant 610058); the Generalitat Valenciana postdoctoral grant APOSTD/2018/177; 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; the Jansky Fellowship program of the National Radio Astronomy Observatory (NRAO); the Japanese Government (Monbukagakusho: MEXT) Scholarship; the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for JSPS Research Fellowship (JP17J08829); JSPS Overseas Research Fellowships; the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (CAS, grants QYZDJ-SSW-SLH057, QYZDJ-SSW-SYS008); 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 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, and 107-2119-M-110-005); the National Aeronautics and Space Administration (NASA, Fermi Guest Investigator grant 80NSSC17K0649); 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-1312651, AST-1337663, AST-1440254, AST-1555365, AST-1715061, AST-1614868, AST-1615796, AST-1716327, OISE-1743747, AST-1816420); the Natural Science Foundation of China (grants 11573051, 11633006, 11650110427, 10625314, 11721303, 11725312, 11873028, 11873073, U1531245, 11473010); 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 Youth Thousand Talents Program of China; the National Research Foundation of Korea (grant 2015-R1D1A1A01056807, the Global PhD Fellowship Grant: NRF-2015H1A2A1033752, and the Korea Research Fellowship Program: NRF-2015H1D3A1066561); 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 Technology (DST) of South Africa; 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 Canada and by the Province of Ontario through the Ministry of Economic Development, Job Creation and Trade); the Russian Science Foundation (grant 17-12-01029); the Spanish Ministerio de Economía y Competitividad (grants AYA2015-63939-C2-1-P, AYA2016-80889-P); 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 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 Italian Ministero dell'Istruzione Università e Ricerca through the grant Progetti Premiali 2012-iALMA (CUP C52I13000140001); ALMA North America Development Fund; the European Union's Horizon 2020 research and innovation programme under grant agreement No 730562 RadioNet; Chandra TM6-17006X. 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 wish to thank Eric W. Greisen for extending the capabilities of the AIPS software package, which made it possible to handle the wide-bandwidth EHT data. We acknowledge George Moellenbrock for his invaluable contribution to the CASA VLBI upgrade. We thank the staff at the participating observatories, correlation centers, and institutions for their enthusiastic support. This Letter 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. 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 project is a joint effort of the Instituto Nacional de Astrófisica, Óptica, y Electrónica (Mexico) and the University of Massachusetts at Amherst (USA). 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. Partial SPT support is provided by the NSF Physics Frontier Center award (PHY-0114422) to the Kavli Institute of Cosmological Physics at the University of Chicago (USA), the Kavli Foundation, and the GBMF (GBMF-947). The SPT hydrogen maser was provided on loan from the GLT, courtesy of ASIAA. 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 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 - , IRAM:30 m - , JCMT - , LMT - , SMA - , ARO:SMT - , SPT - . Software: DiFX (Deller et al. 2011), CALC, PolConvert (Martí-Vidal et al. 2016), HOPS (Whitney et al. 2004), CASA (McMullin et al. 2007), AIPS (Greisen 2003), ParselTongue (Kettenis et al. 2006), GNU Parallel (Tange 2011), GILDAS, eht-imaging (Chael et al. 2016, 2018), 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).
Funders:
Funding AgencyGrant Number
Academy of Finland274477
Academy of Finland284495
Academy of Finland312496
European Research Council (ERC)731016
Alexander von Humboldt FoundationUNSPECIFIED
Harvard UniversityUNSPECIFIED
John Templeton Foundation60477
China Scholarship CouncilUNSPECIFIED
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)PIA ACT172033
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1171506
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)BASAL AFB-170002
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)31140007
Consejo Nacional de Ciencia y Tecnología (CONACYT)104497
Consejo Nacional de Ciencia y Tecnología (CONACYT)275201
Consejo Nacional de Ciencia y Tecnología (CONACYT)279006
Consejo Nacional de Ciencia y Tecnología (CONACYT)281692
Delaney Family John A. Wheeler ChairUNSPECIFIED
Perimeter InstituteUNSPECIFIED
Dirección General de Asuntos del Personal Académico-Universidad Nacional Autónoma de MéxicoIN112417
European Research Council (ERC)610058
Generalitat ValencianaAPOSTD/2018/177
Gordon and Betty Moore FoundationGBMF-3561
Gordon and Betty Moore FoundationGBMF-5278
Istituto Nazionale di Fisica Nucleare (INFN)UNSPECIFIED
International Max Planck Research School for Astronomy and AstrophysicsUNSPECIFIED
University of BonnUNSPECIFIED
University of CologneUNSPECIFIED
Jansky FellowshipUNSPECIFIED
National Radio Astronomy ObservatoryUNSPECIFIED
MonbukagakushoUNSPECIFIED
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Japan Society for the Promotion of Science (JSPS)JP17J08829
Key Research Program of Frontier SciencesUNSPECIFIED
Chinese Academy of SciencesQYZDJ-SSW-SLH057
Chinese Academy of SciencesQYZDJ-SSW-SYS008
Leverhulme TrustUNSPECIFIED
Max-Planck-Gesellschaft (MPG)UNSPECIFIED
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
Massachusetts Institute of Technology (MIT)UNSPECIFIED
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
NASA80NSSC17K0649
National Institute of Natural Sciences (NINS)UNSPECIFIED
National Key Research and Development Program of China2016YFA0400704
National Key Research and Development Program of China2016YFA0400702
NSFAST-0096454
NSFAST-0352953
NSFAST-0521233
NSFAST-0705062
NSFAST-0905844
NSFAST-0922984
NSFAST-1126433
NSFAST-1140030
NSF Graduate Research FellowshipDGE-1144085
NSFAST-1207704
NSFAST-1207730
NSFAST-1207752
NSFMRI-1228509
NSFOPP-1248097
NSFAST-1310896
NSFAST-1312651
NSFAST-1337663
NSFAST-1440254
NSFAST-1555365
NSFAST-1715061
NSFAST-1615796
NSFAST-1614868
NSFAST-1716327
NSFOISE-1743747
NSFAST-1816420
Natural Science Foundation of China11573051
Natural Science Foundation of China11633006
Natural Science Foundation of China11650110427
Natural Science Foundation of China10625314
Natural Science Foundation of China11721303
Natural Science Foundation of China11725312
Natural Science Foundation of China11873028
Natural Science Foundation of China11873073
Natural Science Foundation of ChinaU1531245
Natural Science Foundation of China11473010
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
National Youth Thousand Talents Program of ChinaUNSPECIFIED
National Research Foundation of Korea2015-R1D1A1A01056807
National Research Foundation of KoreaNRF-2015H1A2A1033752
National Research Foundation of KoreaNRF-2015H1D3A1066561
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)639.043.513
Spinoza PrizeSPI 78-409
South African Radio Astronomy Observatory (SARAO)UNSPECIFIED
National Research Foundation (South Africa)UNSPECIFIED
Department of Science and Technology (South Africa)UNSPECIFIED
Onsala Space Observatory (OSO)UNSPECIFIED
Swedish Research Council2017-00648
Government of CanadaUNSPECIFIED
Department of Innovation, Science and Economic Development (Canada)UNSPECIFIED
Province of Ontario Ministry of Economic Development, Job Creation and TradeUNSPECIFIED
Russian Science Foundation17-12-01029
Ministerio de Economía y Competitividad (MINECO)AYA2015-63939-C2-1-P
Ministerio de Economía y Competitividad (MINECO)AYA2016-80889-P
Severo OchoaSEV-2017-0709
Toray Science FoundationUNSPECIFIED
Department of Energy (DOE)89233218CNA000001
Ministero dell'Istruzione, Università e Ricerca (MIUR)CUP C52I13000140001
European Research Council (ERC)730562 RadioNet
ALMA North America Development FundUNSPECIFIED
NASA ChandraTM6-17006X
NSFACI-1548562
NSFDBI-0735191
NSFDBI-1265383
NSFDBI-1743442
NSFTG-AST170024
NSFTG-AST080026N
NSFAST-170028
Compute OntarioUNSPECIFIED
Calcul QuebecUNSPECIFIED
Compute CanadaUNSPECIFIED
Smithsonian InstitutionUNSPECIFIED
Academia SinicaUNSPECIFIED
National Key Research and Development Program of China2017YFA0402700
Science and Technology Facilities Council (STFC)UNSPECIFIED
State of ArizonaUNSPECIFIED
NSFPHY-0114422
Kavli FoundationUNSPECIFIED
Gordon and Betty Moore FoundationGBMF 947
NSFPLR-1248097
NSFPHY-1125897
Subject Keywords:black hole physics – galaxies: individual (M87, 3C279) – galaxies: jets – techniques: high angular resolution – techniques: interferometric
Issue or Number:1
Record Number:CaltechAUTHORS:20190410-102159947
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190410-102159947
Official Citation:The Event Horizon Telescope Collaboration et al 2019 ApJL 875 L3
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94617
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Apr 2019 17:46
Last Modified:03 Oct 2019 21:05

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