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Imaging the Schwarzschild-radius-scale Structure of M87 with the Event Horizon Telescope Using Sparse Modeling

Akiyama, Kazunori and Kuramochi, Kazuki and Ikeda, Shiro and Fish, Vincent L. and Tazaki, Fumie and Honma, Mareki and Doeleman, Sheperd S. and Broderick, Avery E. and Dexter, Jason and Mościbrodzka, Monika and Bouman, Katherine L. and Chael, Andrew A. and Zaizen, Masamichi (2017) Imaging the Schwarzschild-radius-scale Structure of M87 with the Event Horizon Telescope Using Sparse Modeling. Astrophysical Journal, 838 (1). Art. No. 1. ISSN 1538-4357. doi:10.3847/1538-4357/aa6305.

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We propose a new imaging technique for radio and optical/infrared interferometry. The proposed technique reconstructs the image from the visibility amplitude and closure phase, which are standard data products of short-millimeter very long baseline interferometers such as the Event Horizon Telescope (EHT) and optical/infrared interferometers, by utilizing two regularization functions: the ℓ_1-norm and total variation (TV) of the brightness distribution. In the proposed method, optimal regularization parameters, which represent the sparseness and effective spatial resolution of the image, are derived from data themselves using cross-validation (CV). As an application of this technique, we present simulated observations of M87 with the EHT based on four physically motivated models. We confirm that ℓ_1 + TV regularization can achieve an optimal resolution of ~20%–30% of the diffraction limit λ/D_(max), which is the nominal spatial resolution of a radio interferometer. With the proposed technique, the EHT can robustly and reasonably achieve super-resolution sufficient to clearly resolve the black hole shadow. These results make it promising for the EHT to provide an unprecedented view of the event-horizon-scale structure in the vicinity of the supermassive black hole in M87 and also the Galactic center Sgr A*.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Akiyama, Kazunori0000-0002-9475-4254
Fish, Vincent L.0000-0002-7128-9345
Honma, Mareki0000-0003-4058-9000
Doeleman, Sheperd S.0000-0002-9031-0904
Broderick, Avery E.0000-0002-3351-760X
Dexter, Jason0000-0003-3903-0373
Bouman, Katherine L.0000-0003-0077-4367
Chael, Andrew A.0000-0003-2966-6220
Additional Information:© 2017. The American Astronomical Society. Received 2016 November 1; revised 2017 February 17; accepted 2017 February 23; published 2017 March 17. We thank the anonymous referee for useful and constructive suggestions to improve the paper. K.A. thanks Dr. Michael D. Johnson and Dr. Lindy Blackburn for many useful suggestions on this work. K.A. and this work are financially supported by the program of Postdoctoral Fellowships for Research Abroad at the Japan Society for the Promotion of Science. A.E.B. receives financial support from the Perimeter Institute for Theoretical Physics and the Natural Sciences and Engineering Research Council of Canada through a Discovery Grant. M.M. acknowledges support from the ERC Synergy Grant (Grant 610058). Event Horizon Telescope work at MIT Haystack Observatory and the Harvard Smithsonian Center for Astrophysics is supported by grants from the National Science Foundation (NSF; AST-1440254, AST-1614868) and through an award from the Gordon and Betty Moore Foundation (GMBF-3561). Work on sparse modeling and Event Horizon Telescope at the Mizusawa VLBI Observatory, National Astronomical Observatory of Japan is financially supported by the MEXT/JSPS KAKENHI Grant Numbers 24540242, 25120007, and 25120008. Research at Perimeter Institute is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Research and Innovation. Software: MAPS (, CASA.
Funding AgencyGrant Number
Perimeter Institute for Theoretical PhysicsUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
European Research Council (ERC)610058
Gordon and Betty Moore FoundationGMBF-3561
Japan Society for the Promotion of Science (JSPS)24540242
Japan Society for the Promotion of Science (JSPS)25120007
Japan Society for the Promotion of Science (JSPS)25120008
Industry CanadaUNSPECIFIED
Ontario Ministry of Research and InnovationUNSPECIFIED
Subject Keywords:accretion, accretion disks; black hole physics; Galaxy: center; submillimeter: general; techniques: interferometric
Issue or Number:1
Record Number:CaltechAUTHORS:20190405-150443958
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Official Citation:Kazunori Akiyama et al 2017 ApJ 838 1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94515
Deposited By: George Porter
Deposited On:05 Apr 2019 22:48
Last Modified:16 Nov 2021 17:05

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