IMAGING AN EVENT HORIZON: MITIGATION OF SOURCE VARIABILITY OF SAGITTARIUS A*
The black hole in the center of the Galaxy, associated with the compact source Sagittarius A* (Sgr A*), is predicted to cast a shadow upon the emission of the surrounding plasma flow, which encodes the influence of general relativity (GR) in the strong-field regime. The Event Horizon Telescope (EHT)...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | en_US |
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IOP Publishing
2017
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| Online Access: | http://hdl.handle.net/1721.1/109451 |
| _version_ | 1811089716726988800 |
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| author | Roelofs, Freek Shiokawa, Hotaka Gammie, Charles F. Falcke, Heino Krichbaum, Thomas P. Zensus, J. Anton Lu, Rusen Fish, Vincent L. Doeleman, Sheperd Samuel |
| author2 | Haystack Observatory |
| author_facet | Haystack Observatory Roelofs, Freek Shiokawa, Hotaka Gammie, Charles F. Falcke, Heino Krichbaum, Thomas P. Zensus, J. Anton Lu, Rusen Fish, Vincent L. Doeleman, Sheperd Samuel |
| author_sort | Roelofs, Freek |
| collection | MIT |
| description | The black hole in the center of the Galaxy, associated with the compact source Sagittarius A* (Sgr A*), is predicted to cast a shadow upon the emission of the surrounding plasma flow, which encodes the influence of general relativity (GR) in the strong-field regime. The Event Horizon Telescope (EHT) is a Very Long Baseline Interferometry (VLBI) network with a goal of imaging nearby supermassive black holes (in particular Sgr A* and M87) with angular resolution sufficient to observe strong gravity effects near the event horizon. General relativistic magnetohydrodynamic (GRMHD) simulations show that radio emission from Sgr A* exhibits variability on timescales of minutes, much shorter than the duration of a typical VLBI imaging experiment, which usually takes several hours. A changing source structure during the observations, however, violates one of the basic assumptions needed for aperture synthesis in radio interferometry imaging to work. By simulating realistic EHT observations of a model movie of Sgr A*, we demonstrate that an image of the average quiescent emission, featuring the characteristic black hole shadow and photon ring predicted by GR, can nonetheless be obtained by observing over multiple days and subsequent processing of the visibilities (scaling, averaging, and smoothing) before imaging. Moreover, it is shown that this procedure can be combined with an existing method to mitigate the effects of interstellar scattering. Taken together, these techniques allow the black hole shadow in the Galactic center to be recovered on the reconstructed image. |
| first_indexed | 2024-09-23T14:23:35Z |
| format | Article |
| id | mit-1721.1/109451 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T14:23:35Z |
| publishDate | 2017 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | mit-1721.1/1094512022-09-29T09:11:04Z IMAGING AN EVENT HORIZON: MITIGATION OF SOURCE VARIABILITY OF SAGITTARIUS A* Roelofs, Freek Shiokawa, Hotaka Gammie, Charles F. Falcke, Heino Krichbaum, Thomas P. Zensus, J. Anton Lu, Rusen Fish, Vincent L. Doeleman, Sheperd Samuel Haystack Observatory Lu, Rusen Fish, Vincent L. Doeleman, Sheperd Samuel The black hole in the center of the Galaxy, associated with the compact source Sagittarius A* (Sgr A*), is predicted to cast a shadow upon the emission of the surrounding plasma flow, which encodes the influence of general relativity (GR) in the strong-field regime. The Event Horizon Telescope (EHT) is a Very Long Baseline Interferometry (VLBI) network with a goal of imaging nearby supermassive black holes (in particular Sgr A* and M87) with angular resolution sufficient to observe strong gravity effects near the event horizon. General relativistic magnetohydrodynamic (GRMHD) simulations show that radio emission from Sgr A* exhibits variability on timescales of minutes, much shorter than the duration of a typical VLBI imaging experiment, which usually takes several hours. A changing source structure during the observations, however, violates one of the basic assumptions needed for aperture synthesis in radio interferometry imaging to work. By simulating realistic EHT observations of a model movie of Sgr A*, we demonstrate that an image of the average quiescent emission, featuring the characteristic black hole shadow and photon ring predicted by GR, can nonetheless be obtained by observing over multiple days and subsequent processing of the visibilities (scaling, averaging, and smoothing) before imaging. Moreover, it is shown that this procedure can be combined with an existing method to mitigate the effects of interstellar scattering. Taken together, these techniques allow the black hole shadow in the Galactic center to be recovered on the reconstructed image. 2017-05-31T13:55:20Z 2017-05-31T13:55:20Z 2016-01 2015-07 Article http://purl.org/eprint/type/JournalArticle 1538-4357 http://hdl.handle.net/1721.1/109451 Lu, Ru-Sen et al. “IMAGING AN EVENT HORIZON: MITIGATION OF SOURCE VARIABILITY OF SAGITTARIUS A*.” The Astrophysical Journal 817.2 (2016): 173. © 2016 The American Astronomical Society en_US http://dx.doi.org/10.3847/0004-637x/817/2/173 The Astrophysical Journal Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf IOP Publishing IOP Publishing |
| spellingShingle | Roelofs, Freek Shiokawa, Hotaka Gammie, Charles F. Falcke, Heino Krichbaum, Thomas P. Zensus, J. Anton Lu, Rusen Fish, Vincent L. Doeleman, Sheperd Samuel IMAGING AN EVENT HORIZON: MITIGATION OF SOURCE VARIABILITY OF SAGITTARIUS A* |
| title | IMAGING AN EVENT HORIZON: MITIGATION OF SOURCE VARIABILITY OF SAGITTARIUS A* |
| title_full | IMAGING AN EVENT HORIZON: MITIGATION OF SOURCE VARIABILITY OF SAGITTARIUS A* |
| title_fullStr | IMAGING AN EVENT HORIZON: MITIGATION OF SOURCE VARIABILITY OF SAGITTARIUS A* |
| title_full_unstemmed | IMAGING AN EVENT HORIZON: MITIGATION OF SOURCE VARIABILITY OF SAGITTARIUS A* |
| title_short | IMAGING AN EVENT HORIZON: MITIGATION OF SOURCE VARIABILITY OF SAGITTARIUS A* |
| title_sort | imaging an event horizon mitigation of source variability of sagittarius a |
| url | http://hdl.handle.net/1721.1/109451 |
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