Origin of the Local Group satellite planes

Understand

We attempt to understand the planes of satellite galaxies orbiting the Milky Way (MW) and M31 in the context of Modified Newtonian Dynamics (MOND), which implies a close MW-M31 flyby occurred ${\approx 8}$ Gyr ago.

• Using the timing argument, we obtain MW-M31 trajectories consistent with cosmological initial conditions and present observations.
• We adjust the present M31 proper motion within its uncertainty in order to simulate a range of orbital geometries and closest approach distances.
• Treating the MW and M31 as point masses, we follow the trajectories of surrounding test particle disks, thereby mapping out the tidal debris distribution.