Imaging the Schwarzschild-radius-scale Structure of M87 with the Event Horizon Telescope Using Sparse Modeling
Author(s)Kuramochi, Kazuki; Ikeda, Shiro; Tazaki, Fumie; Honma, Mareki; E. Broderick, Avery; Dexter, Jason; Mościbrodzka, Monika; A. Chael, Andrew; Zaizen, Masamichi; Akiyama, Kazunori; Bouman, Katherine L; Fish, Vincent L.; Doeleman, Sheperd Samuel; ... Show more Show less
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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 [subscript 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 [subscript 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*.
DepartmentHaystack Observatory; Massachusetts Institute of Technology. Computer Science and Artificial Intelligence Laboratory; Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Akiyama, Kazunori, Kazuki Kuramochi, Shiro Ikeda, Vincent L. Fish, Fumie Tazaki, Mareki Honma, Sheperd S. Doeleman, et al. “Imaging the Schwarzschild-Radius-Scale Structure of M87 with the Event Horizon Telescope Using Sparse Modeling.” The Astrophysical Journal 838, no. 1 (March 17, 2017): 1. © 2017 The American Astronomical Society
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