Journal Article

The role of large-scale magnetic fields in galaxy NGC 891: can magnetic fields help to reduce the local mass-to-light ratio in the galactic outskirts?

Joanna Jałocha, Łukasz Bratek, Jan Pȩkala and Marek Kutschera

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 421, issue 3, pages 2155-2160
Published in print April 2012 | ISSN: 0035-8711
Published online April 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.20447.x
The role of large-scale magnetic fields in galaxy NGC 891: can magnetic fields help to reduce the local mass-to-light ratio in the galactic outskirts?

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We address the problem of the influence of large-scale magnetic fields on galactic rotation for the example of the spiral galaxy NGC 891. Based on its rotation curve and the surface density of H i we determine, in the framework of the global disc model, the surface density of matter. Then, based on the surface brightness, we determine the corresponding profile of the local mass-to-light ratio. We also model the vertical gradient of azimuthal velocity in the quasi-circular-orbit approximation, and compare it with measurements. We discuss what factors may influence the rotation of matter in NGC 891 and how this can translate to changes in the profile of the local mass-to-light ratio. In particular, we discuss the possible effect of magnetic fields on the motion of ionized gas, and, consequently, on the determination of the profile of the local mass-to-light ratio. Finally, we put forward the hypothesis that the asymmetry in magnetic fields observed in NGC 891 might be responsible for the observed anomalous behaviour of the vertical gradient.

Keywords: galaxies: individual: NGC 891; galaxies: kinematics and dynamics; galaxies: magnetic fields; galaxies: spiral; galaxies: structure

Journal Article.  3971 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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