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?

TL;DR

This paper investigates how large-scale magnetic fields in galaxy NGC 891 influence its rotation and the local mass-to-light ratio, proposing magnetic fields as a factor in observed anomalies in galactic dynamics.

Contribution

It models the impact of magnetic fields on galactic rotation and mass-to-light ratio profiles, linking magnetic asymmetries to observed velocity gradient anomalies.

Findings

Magnetic fields can significantly affect the motion of ionized gas in NGC 891.

Asymmetries in magnetic fields may explain anomalous vertical velocity gradients.

Magnetic influence could help reconcile discrepancies in mass-to-light ratio measurements.

Abstract

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 HI 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.