Dark Halos of M31 and the Milky Way

Understand

Grand rotation curves (GRC) within ~400 kpc of M31 and the Milky Way were constructed by combining disk rotation velocities and radial velocities of satellite galaxies and globular clusters.

• The GRC for the Milky Way was revised using the most recent Solar rotation velocity.
• The derived GRCs were deconvolved into a de Vaucouleurs bulge, exponential disk, and a dark halo with the Navarro-Frenk-White (NFW) density profile by the least chi-squares fitting.
• Comparison of the best-fit parameters revealed similarity of the disks and bulges of the two galaxies, whereas the dark halo mass of M31 was found to be twice the Galaxy's.