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Published May 2020 | Published
Journal Article Open

Linear polarization in the nucleus of M87 at 7 mm and 1.3 cm


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.

Additional Information

© 2020 ESO. Article published by EDP Sciences. Received 13 December 2019; Accepted 24 April 2020; Published online 15 May 2020. We thank the anonymous referee and Svetlana Jorstad for comprehensive comments and suggestions that helped to improve the manuscript. This study makes use of 43 GHz VLBA data from the VLBA-BU Blazar Monitoring Program (VLBA-BU-BLAZAR; http://www.bu.edu/blazars/VLBAproject.html), funded by NASA through the Fermi Guest Investigator Program. The VLBA is an instrument of the National Radio Astronomy Observatory. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated by Associated Universities, Inc. This work made use of the Swinburne University of Technology software correlator, developed as part of the Australian Major National Research Facilities Programme and operated under licence.

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August 19, 2023
October 20, 2023