Effect of magnetic field on the rotation curves of spiral galaxies

Abstract

Discrepancies between expected and observed rotation curves in spiral galaxies are commonly interpreted as evidence for the existence of dark matter. Dark matter can explain the observed flat rotation curves at the outer radii. However, some rotation curves of spiral galaxies exhibit rising features at large distances from the galactic centers that cannot be attributed to dark matter alone. Addition of magnetic field contribution to the rotation curves of spiral galaxies has been proposed in some literature to explain the rising features. In this work we investigated the rotation curves of three spiral galaxies, i.e. NGC 2841, NGC 6946, and M 31, whose profiles of azimuthal magnetic field are available in literature. In general, decomposition scenarios using four components (stellar disk, gas, bulge, and dark matter halo) with magnetic field fit better to the observational data.