Journal
ASTROPHYSICAL JOURNAL
Volume 858, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.3847/1538-4357/aab6b5
Keywords
accretion, accretion disks; black hole physics; Galaxy: center; techniques: high angular resolution; techniques: image processing; techniques: interferometric
Categories
Funding
- MEXT/JSPS KAKENHI [24540242, 25120007, 25120008]
- National Science Foundation [AST-1614868]
- program of the Jansky Fellowship of the National Radio Astronomy Observatory
- NSF [AST-1614868, AST-1440254]
- Gordon and Betty Moore Foundation [GMBF-3561]
- John Templeton Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1614868] Funding Source: National Science Foundation
- Grants-in-Aid for Scientific Research [24540242, 15K21718] Funding Source: KAKEN
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We propose a new imaging technique for interferometry using sparse modeling, utilizing two regularization terms: the l(1)-norm and a new function named total squared variation (TSV) of the brightness distribution. First, we demonstrate that our technique may achieve a supen-esolution of similar to 30% compared with the traditional CLEAN beam size using synthetic observations of two point sources. Second, we present simulated observations of three physically motivated static models of Sgr A* with the Event Horizon Telescope (EHT) to show the performance of proposed techniques in greater detail. Remarkably, in both the image and gradient domains, the optimal beam size minimizing root-mean-squared errors is less than or similar to 10% of the traditional CLEAN beam size for l(1)-FTSV regularization, and non-convolved reconstructed images have smaller errors than beam-convolved reconstructed images. This indicates that TSV is well matched to the expected physical properties of the astronomical images and the traditional post-processing technique of Gaussian convolution in interferometric imaging may not be required. We also propose a feature-extraction method to detect circular features from the image of a black hole shadow and use it to evaluate the performance of the image reconstruction. With this method and reconstructed images, the EHT can constrain the radius of the black hole shadow with an accuracy of similar to 10%-20% in present simulations for Sgr A*, suggesting that the EHT would be able to provide useful independent measurements of the mass of the supermassive black holes in Sgr A* and also another primary target, M87.
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