Polarization Monitoring of the Lens System JVAS B0218+357
Monitoring of the lens system JVAS B0218+357 with the Fermi Gamma-ray Space Telescope measured a different time delay to that derived from radio observations. We have re-analysed three months of archival Very Large Array data to produce variability curves with an average sampling of one epoch per da...
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| Format: | Article |
| Language: | English |
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MDPI AG
2017-10-01
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| Series: | Galaxies |
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| Online Access: | https://www.mdpi.com/2075-4434/5/4/69 |
| _version_ | 1819109660603449344 |
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| author | Andrew Biggs Ian Browne |
| author_facet | Andrew Biggs Ian Browne |
| author_sort | Andrew Biggs |
| collection | DOAJ |
| description | Monitoring of the lens system JVAS B0218+357 with the Fermi Gamma-ray Space Telescope measured a different time delay to that derived from radio observations. We have re-analysed three months of archival Very Large Array data to produce variability curves with an average sampling of one epoch per day in total flux, polarized flux and polarization position angle (PPA) at 15, 8.4 and 5 GHz. The variability is particularly strong in polarized flux. Dense sampling and improved subtraction of the Einstein ring has allowed us to produce superior variability curves and a preliminary analysis has resulted in a time delay (11.5 days) which agrees well with the γ -ray value. Both images of 0218+357 are subject to strong Faraday rotation and depolarization as a result of the radio waves passing through the interstellar medium of the spiral lens galaxy. Our data reveal frequency-dependent variations in the PPA that are different in each image and which must therefore result from variable Faraday rotation in the lens galaxy on timescales of a few days. Our analysis has revealed systematic errors in the polarization position angle measurements that strongly correlate with hour angle. Although we have been able to correct for these, we caution that all VLA polarization observations are potentially affected. |
| first_indexed | 2024-12-22T03:29:22Z |
| format | Article |
| id | doaj.art-48429f72a7d44d678cbf9e66378e1f97 |
| institution | Directory Open Access Journal |
| issn | 2075-4434 |
| language | English |
| last_indexed | 2024-12-22T03:29:22Z |
| publishDate | 2017-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Galaxies |
| spelling | doaj.art-48429f72a7d44d678cbf9e66378e1f972022-12-21T18:40:32ZengMDPI AGGalaxies2075-44342017-10-01546910.3390/galaxies5040069galaxies5040069Polarization Monitoring of the Lens System JVAS B0218+357Andrew Biggs0Ian Browne1European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching bei München, GermanyJodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics & Astronomy, The University of Manchester, Oxford Road, M13 9PL Manchester, UKMonitoring of the lens system JVAS B0218+357 with the Fermi Gamma-ray Space Telescope measured a different time delay to that derived from radio observations. We have re-analysed three months of archival Very Large Array data to produce variability curves with an average sampling of one epoch per day in total flux, polarized flux and polarization position angle (PPA) at 15, 8.4 and 5 GHz. The variability is particularly strong in polarized flux. Dense sampling and improved subtraction of the Einstein ring has allowed us to produce superior variability curves and a preliminary analysis has resulted in a time delay (11.5 days) which agrees well with the γ -ray value. Both images of 0218+357 are subject to strong Faraday rotation and depolarization as a result of the radio waves passing through the interstellar medium of the spiral lens galaxy. Our data reveal frequency-dependent variations in the PPA that are different in each image and which must therefore result from variable Faraday rotation in the lens galaxy on timescales of a few days. Our analysis has revealed systematic errors in the polarization position angle measurements that strongly correlate with hour angle. Although we have been able to correct for these, we caution that all VLA polarization observations are potentially affected.https://www.mdpi.com/2075-4434/5/4/69gravitational lensingcosmology |
| spellingShingle | Andrew Biggs Ian Browne Polarization Monitoring of the Lens System JVAS B0218+357 Galaxies gravitational lensing cosmology |
| title | Polarization Monitoring of the Lens System JVAS B0218+357 |
| title_full | Polarization Monitoring of the Lens System JVAS B0218+357 |
| title_fullStr | Polarization Monitoring of the Lens System JVAS B0218+357 |
| title_full_unstemmed | Polarization Monitoring of the Lens System JVAS B0218+357 |
| title_short | Polarization Monitoring of the Lens System JVAS B0218+357 |
| title_sort | polarization monitoring of the lens system jvas b0218 357 |
| topic | gravitational lensing cosmology |
| url | https://www.mdpi.com/2075-4434/5/4/69 |
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