On the Maximum Contribution of Magnetic Field to the Rotation Curves of Dwarf Spiral Galaxies

Dark matter is usually considered responsible for the flat rotation curves observed at the outer radii of spiral galaxies. Since the existence of dark matter has not been indisputably detected by experiments, magnetic field is sometimes proposed to be substitute for dark matter in explaining the shape of rotation curves of spiral galaxies. Magnetic field that interacts with cosmic rays generates pressure, which in turn accelerates gas flow/dynamics and affects the speed of gas rotation. Some other studies discuss the possibilities that the flat or even increased rotation curves at the outer radii may be attributed both to dark matter and the galactic magnetic fields. In this work, we examined 16 rotation curve data of dwarf spiral galaxies in the Spitzer Photometry and Accurate Rotation Curves (SPARC) catalog obtained by Spitzer in 3.6 mu m. We find that the shape of the rotation curves of the dwarf spiral galaxies cannot be explained by the contribution of magnetic field alone, due to stability issues. However, adding some contribution of magnetic field to the dark matter component explains the rotation curves at the large radii better, compared to dark matter without magnetic field. We therefore determined the maximum contribution of the magnetic field for the 16 dwarf spiral galaxies.