The Clustering of Orbital Poles Induced by the LMC: Hints for the Origin of Planes of Satellites

A significant fraction of Milky Way (MW) satellites exhibit phase-space properties consistent with a coherent orbital plane. Using tailored N-body simulations of a spherical MW halo that recently captured a massive (1.8 x 10(11) M-circle dot) LMC-like satellite, we identify the physical mechanisms that may enhance the clustering of orbital poles of objects orbiting the MW. The LMC deviates the orbital poles of MW dark matter particles from the present-day random distribution. Instead, the orbital poles of particles beyond R approximate to 50 kpc cluster near the present-day orbital pole of the LMC along a sinusoidal pattern across the sky. The density of orbital poles is enhanced near the LMC by a factor delta rho(max) = 30% (50%) with respect to underdense regions and delta rho(iso) = 15% (30%) relative to the isolated MW simulation (no LMC) between 50 and 150 kpc (150-300 kpc). The clustering appears after the LMC's pericenter (approximate to 50Myr ago, 49 kpc) and lasts for at least 1 Gyr. Clustering occurs because of three effects: (1) the LMC shifts the velocity and position of the central density of the MW's halo and disk; (2) the dark matter dynamical friction wake and collective response induced by the LMC change the kinematics of particles; (3) observations of particles selected within spatial planes suffer from a bias, such that measuring orbital poles in a great circle in the sky enhances the probability of their orbital poles being clustered. This scenario should be ubiquitous in hosts that recently captured a massive satellite (at least approximate to 1:10mass ratio), causing the clustering of orbital poles of halo tracers.

Automated summary

By simulating a LMC-like satellite, it was found that LMC can cause the clustering of orbital poles of MW dark matter particles, which lasts for at least 1 Gyr.