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| Main Authors: | , , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2023
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| Online Access: | https://arxiv.org/abs/2312.08643 |
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| _version_ | 1866914727177748480 |
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| author | Cho, Ilje Gómez, José L. Lico, Rocco Zhao, Guang-Yao Traianou, Efthalia Dahale, Rohan Fuentes, Antonio Toscano, Teresa Foschi, Marianna Kovalev, Yuri Y. Lobanov, Andrei Pushkarev, Alexander B. Gurvits, Leonid I. Kim, Jae-Young Lisakov, Mikhail Voitsik, Petr Myserlis, Ioannis Pötzl, Felix Ros, Eduardo |
| author_facet | Cho, Ilje Gómez, José L. Lico, Rocco Zhao, Guang-Yao Traianou, Efthalia Dahale, Rohan Fuentes, Antonio Toscano, Teresa Foschi, Marianna Kovalev, Yuri Y. Lobanov, Andrei Pushkarev, Alexander B. Gurvits, Leonid I. Kim, Jae-Young Lisakov, Mikhail Voitsik, Petr Myserlis, Ioannis Pötzl, Felix Ros, Eduardo |
| contents | We present total intensity and linear polarization images of OJ287 at 1.68GHz, obtained through space-based VLBI observations with RadioAstron on April 16, 2016. The observations were conducted using a ground array consisting of the VLBA and the EVN. Ground-space fringes were detected with a maximum projected baseline length of 5.6 Earth's diameter, resulting in an angular resolution of 530 uas. With this unprecedented resolution at such a low frequency, the progressively bending jet structure of OJ287 has been resolved up to 10 pc of the projected distance from the radio core. In comparison with close-in-time VLBI observations at 15, 43, 86 GHz from MOJAVE and VLBA-BU-BLAZAR monitoring projects, we obtain the spectral index map showing the opaque core and optically thin jet components. The optically thick core has a brightness temperature of 10$^{13}$ K, and is further resolved into two sub-components at higher frequencies labeled C1 and C2. These sub-components exhibit a transition from optically thick to thin, with a SSA turnover frequency estimated to be 33 and 11.5 GHz, and a turnover flux density 4 and 0.7 Jy, respectively. Assuming a Doppler boosting factor of 10, the SSA values provide the estimate of the magnetic field strengths from SSA of 3.4 G for C1 and 1.0 G for C2. The magnetic field strengths assuming equipartition arguments are also estimated as 2.6 G and 1.6 G, respectively. The integrated degree of linear polarization is found to be approximately 2.5 %, with the electric vector position angle being well aligned with the local jet direction at the core region. This alignment suggests a predominant toroidal magnetic field, which is in agreement with the jet formation model that requires a helical magnetic field anchored to either the black hole ergosphere or the accretion disk. Further downstream, the jet seems to be predominantly threaded by a poloidal magnetic field. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2312_08643 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Unveiling the Bent Jet Structure and Polarization of OJ 287 at 1.7 GHz with Space VLBI Cho, Ilje Gómez, José L. Lico, Rocco Zhao, Guang-Yao Traianou, Efthalia Dahale, Rohan Fuentes, Antonio Toscano, Teresa Foschi, Marianna Kovalev, Yuri Y. Lobanov, Andrei Pushkarev, Alexander B. Gurvits, Leonid I. Kim, Jae-Young Lisakov, Mikhail Voitsik, Petr Myserlis, Ioannis Pötzl, Felix Ros, Eduardo High Energy Astrophysical Phenomena We present total intensity and linear polarization images of OJ287 at 1.68GHz, obtained through space-based VLBI observations with RadioAstron on April 16, 2016. The observations were conducted using a ground array consisting of the VLBA and the EVN. Ground-space fringes were detected with a maximum projected baseline length of 5.6 Earth's diameter, resulting in an angular resolution of 530 uas. With this unprecedented resolution at such a low frequency, the progressively bending jet structure of OJ287 has been resolved up to 10 pc of the projected distance from the radio core. In comparison with close-in-time VLBI observations at 15, 43, 86 GHz from MOJAVE and VLBA-BU-BLAZAR monitoring projects, we obtain the spectral index map showing the opaque core and optically thin jet components. The optically thick core has a brightness temperature of 10$^{13}$ K, and is further resolved into two sub-components at higher frequencies labeled C1 and C2. These sub-components exhibit a transition from optically thick to thin, with a SSA turnover frequency estimated to be 33 and 11.5 GHz, and a turnover flux density 4 and 0.7 Jy, respectively. Assuming a Doppler boosting factor of 10, the SSA values provide the estimate of the magnetic field strengths from SSA of 3.4 G for C1 and 1.0 G for C2. The magnetic field strengths assuming equipartition arguments are also estimated as 2.6 G and 1.6 G, respectively. The integrated degree of linear polarization is found to be approximately 2.5 %, with the electric vector position angle being well aligned with the local jet direction at the core region. This alignment suggests a predominant toroidal magnetic field, which is in agreement with the jet formation model that requires a helical magnetic field anchored to either the black hole ergosphere or the accretion disk. Further downstream, the jet seems to be predominantly threaded by a poloidal magnetic field. |
| title | Unveiling the Bent Jet Structure and Polarization of OJ 287 at 1.7 GHz with Space VLBI |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2312.08643 |