The effect of magnetic field on the inner Galactic rotation curve

TL;DR

This study demonstrates that magnetic fields can significantly influence the inner Galactic rotation curve, potentially eliminating the need for additional mass components like the bulge.

Contribution

It provides a detailed analysis showing magnetic fields' impact on the inner Galaxy's rotation, challenging previous assumptions about the necessity of a bulge component.

Findings

Magnetic fields can account for the inner rotation velocity excess.

The magnetic field strength is constrained to 50-60 μG.

Magnetic effects may reduce the need for a bulge component.

Abstract

In the past few decades, some studies pointed out that magnetic field might affect the rotation curves in galaxies. However, the impact is relatively small compared with the effects of dark matter and the baryonic components. In this letter, we revisit the impact of magnetic field on the rotation curve of our Galaxy. We show that the inner Galactic rotation curve could be affected significantly by the magnetic field. The addition of the inner bulge component, which has been proposed previously to account for the inner rotation curve data, is not necessary. The magnetic field contribution can fully account for the excess of the inner rotation velocity between 5 pc to 50 pc from the Galactic Centre. Our analysis can also constrain the azimuthal component of the central regular magnetic field strength to $B_0 \sim 50-60$ $\mu$G, which is consistent with the observed range.