Volume 637, May 2020
|Number of page(s)||9|
|Section||Letters to the Editor|
|Published online||15 May 2020|
Letter to the Editor
Linear polarization in the nucleus of M87 at 7 mm and 1.3 cm
INAF Istituto di Radioastronomia, Via P. Gobetti 101, Bologna 40129, Italy
2 Astro Space Center, Lebedev Physical Institute, Profsouznaya 84/32, Moscow 117997, Russia
3 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan
4 Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
5 Department of Astronomy, Caltech, Pasadena, CA 91125, USA
6 Jet Propulsion Laboratory, Pasadena, CA 91109, USA
7 Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141 Taipei 10617, Taiwan
8 Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 08826, Republic of Korea
9 National Radio Astronomy Observatory, Socorro, NM 87801, USA
10 National Institute of Technology, Hachinohe College, 16-1 Uwanotai, Tamonoki, Hachinohe City, Aomori Prefecture 039-1192, Japan
Accepted: 24 April 2020
We report on high angular resolution polarimetric observations of the nearby radio galaxy M87 using the Very Long Baseline Array at 24 GHz (λ = 1.3 cm) and 43 GHz (λ = 7 mm) in 2017–2018. New images of the linear polarization substructure in the nuclear region are presented, characterized by a two-component pattern of polarized intensity and smooth rotation of the polarization plane around the 43 GHz core. From a comparison with an analogous dataset from 2007, we find that this global polarization pattern remains stable on a time interval of 11 yr, while showing smaller month-scale variability. We discuss the possible Faraday rotation toward the M87 nucleus at centimeter to millimeter wavelengths. These results can be interpreted in a scenario where the observed polarimetric pattern is associated with the magnetic structure in the confining magnetohydrodynamic wind, which also serves as the source of the observed Faraday rotation.
Key words: galaxies: active / galaxies: jets / galaxies: nuclei / magnetic fields / polarization / galaxies: individual: M87
© ESO 2020
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