HIGH-RESOLUTION LINEAR POLARIMETRIC IMAGING FOR THE EVENT HORIZON TELESCOPE
Images of the linear polarizations of synchrotron radiation around active galactic nuclei (AGNs) highlight their projected magnetic field lines and provide key data for understanding the physics of accretion and outflow from supermassive black holes. The highest-resolution polarimetric images of AGN...
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IOP Publishing
2017
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| Online adgang: | http://hdl.handle.net/1721.1/108194 https://orcid.org/0000-0003-0077-4367 |
| _version_ | 1826189505635287040 |
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| author | Chael, Andrew A. Johnson, Michael D. Narayan, Ramesh Wardle, John F. C. Doeleman, Sheperd Samuel Bouman, Katherine L |
| author2 | Haystack Observatory |
| author_facet | Haystack Observatory Chael, Andrew A. Johnson, Michael D. Narayan, Ramesh Wardle, John F. C. Doeleman, Sheperd Samuel Bouman, Katherine L |
| author_sort | Chael, Andrew A. |
| collection | MIT |
| description | Images of the linear polarizations of synchrotron radiation around active galactic nuclei (AGNs) highlight their projected magnetic field lines and provide key data for understanding the physics of accretion and outflow from supermassive black holes. The highest-resolution polarimetric images of AGNs are produced with Very Long Baseline Interferometry (VLBI). Because VLBI incompletely samples the Fourier transform of the source image, any image reconstruction that fills in unmeasured spatial frequencies will not be unique and reconstruction algorithms are required. In this paper, we explore some extensions of the Maximum Entropy Method (MEM) to linear polarimetric VLBI imaging. In contrast to previous work, our polarimetric MEM algorithm combines a Stokes I imager that only uses bispectrum measurements that are immune to atmospheric phase corruption, with a joint Stokes Q and U imager that operates on robust polarimetric ratios. We demonstrate the effectiveness of our technique on 7 and 3 mm wavelength quasar observations from the VLBA and simulated 1.3 mm Event Horizon Telescope observations of Sgr A* and M87. Consistent with past studies, we find that polarimetric MEM can produce superior resolution compared to the standard CLEAN algorithm, when imaging smooth and compact source distributions. As an imaging framework, MEM is highly adaptable, allowing a range of constraints on polarization structure. Polarimetric MEM is thus an attractive choice for image reconstruction with the EHT. |
| first_indexed | 2024-09-23T08:15:55Z |
| format | Article |
| id | mit-1721.1/108194 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T08:15:55Z |
| publishDate | 2017 |
| publisher | IOP Publishing |
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| spelling | mit-1721.1/1081942022-09-30T08:43:40Z HIGH-RESOLUTION LINEAR POLARIMETRIC IMAGING FOR THE EVENT HORIZON TELESCOPE Chael, Andrew A. Johnson, Michael D. Narayan, Ramesh Wardle, John F. C. Doeleman, Sheperd Samuel Bouman, Katherine L Haystack Observatory Doeleman, Sheperd Samuel Bouman, Katherine L Images of the linear polarizations of synchrotron radiation around active galactic nuclei (AGNs) highlight their projected magnetic field lines and provide key data for understanding the physics of accretion and outflow from supermassive black holes. The highest-resolution polarimetric images of AGNs are produced with Very Long Baseline Interferometry (VLBI). Because VLBI incompletely samples the Fourier transform of the source image, any image reconstruction that fills in unmeasured spatial frequencies will not be unique and reconstruction algorithms are required. In this paper, we explore some extensions of the Maximum Entropy Method (MEM) to linear polarimetric VLBI imaging. In contrast to previous work, our polarimetric MEM algorithm combines a Stokes I imager that only uses bispectrum measurements that are immune to atmospheric phase corruption, with a joint Stokes Q and U imager that operates on robust polarimetric ratios. We demonstrate the effectiveness of our technique on 7 and 3 mm wavelength quasar observations from the VLBA and simulated 1.3 mm Event Horizon Telescope observations of Sgr A* and M87. Consistent with past studies, we find that polarimetric MEM can produce superior resolution compared to the standard CLEAN algorithm, when imaging smooth and compact source distributions. As an imaging framework, MEM is highly adaptable, allowing a range of constraints on polarization structure. Polarimetric MEM is thus an attractive choice for image reconstruction with the EHT. National Science Foundation (U.S.) (AST-1310896) National Science Foundation (U.S.) (AST-1312034) National Science Foundation (U.S.) (AST-1211539) National Science Foundation (U.S.) (AST-1440254) Gordon and Betty Moore Foundation (GBMF-3561) National Science Foundation (U.S.) (CGV-1111415) National Science Foundation (U.S.). Graduate Research Fellowship Program 2017-04-14T20:56:39Z 2017-04-14T20:56:39Z 2016-09 2016-07 Article http://purl.org/eprint/type/JournalArticle 1538-4357 0004-6256 http://hdl.handle.net/1721.1/108194 Chael, Andrew A. et al. “HIGH-RESOLUTION LINEAR POLARIMETRIC IMAGING FOR THE EVENT HORIZON TELESCOPE.” The Astrophysical Journal 829.1 (2016): 11. CrossRef. Web. © 2016 The American Astronomical Society https://orcid.org/0000-0003-0077-4367 en_US http://dx.doi.org/10.3847/0004-637X/829/1/11 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 | Chael, Andrew A. Johnson, Michael D. Narayan, Ramesh Wardle, John F. C. Doeleman, Sheperd Samuel Bouman, Katherine L HIGH-RESOLUTION LINEAR POLARIMETRIC IMAGING FOR THE EVENT HORIZON TELESCOPE |
| title | HIGH-RESOLUTION LINEAR POLARIMETRIC IMAGING FOR THE EVENT HORIZON TELESCOPE |
| title_full | HIGH-RESOLUTION LINEAR POLARIMETRIC IMAGING FOR THE EVENT HORIZON TELESCOPE |
| title_fullStr | HIGH-RESOLUTION LINEAR POLARIMETRIC IMAGING FOR THE EVENT HORIZON TELESCOPE |
| title_full_unstemmed | HIGH-RESOLUTION LINEAR POLARIMETRIC IMAGING FOR THE EVENT HORIZON TELESCOPE |
| title_short | HIGH-RESOLUTION LINEAR POLARIMETRIC IMAGING FOR THE EVENT HORIZON TELESCOPE |
| title_sort | high resolution linear polarimetric imaging for the event horizon telescope |
| url | http://hdl.handle.net/1721.1/108194 https://orcid.org/0000-0003-0077-4367 |
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