Linear polarization in the nucleus of M87 at 7 mm and 1.3 cm
Abstract
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.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- May 2020
- DOI:
- 10.1051/0004-6361/201937315
- arXiv:
- arXiv:2006.07059
- Bibcode:
- 2020A&A...637L...6K
- Keywords:
-
- galaxies: active;
- galaxies: jets;
- galaxies: nuclei;
- magnetic fields;
- polarization;
- galaxies: individual: M87;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 9 pages, including 4 pages of Appendix