On the Effect of the Large Magellanic Cloud on the Orbital Poles of Milky Way Satellite Galaxies

Abstract

The reflex motion and distortion of the Milky Way (MW) halo caused by the infall of a massive Large Magellanic Cloud (LMC) has been demonstrated to result in an excess of orbital poles of dark matter halo particles towards the LMC orbital pole. This was suggested to help explain the observed preference of MW satellite galaxies to co-orbit along the Vast Polar Structure (VPOS). We test this idea by correcting the positions and velocities of the MW satellites for the Galactocentric-distance-dependent shifts inferred from a LMC-infall simulation. While this should substantially reduce the observed clustering of orbital poles if it were mainly caused by the LMC, we instead find that the strong clustering remains preserved. We confirm the initial study's main result with our simulation of an MW-LMC-like interaction, and use it to identify two reasons why this scenario is unable to explain the VPOS: (1) the orbital pole density enhancement in our simulation is very mild (~10% within 50-250 kpc) compared to the observed enhancement (~220-300%), and (2) it is very sensitive to the specific angular momenta (AM) of the simulation particles, with higher AM particles being affected the least. Particles in simulated dark matter halos tend to follow more radial orbits (lower AM), so their orbital poles are more easily affected by small offsets in position and velocity caused by an LMC infall than objects with more tangential velocity (higher AM), such as the observed dwarf galaxies surrounding the MW. The origin of the VPOS thus remains unexplained.

13 pages, 8 figures. Accepted for publication in ApJ

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• Constraining the Milky Way halo kinematics via its Linear Response to the Large Magellanic Cloud
• A portrait of the Vast Polar Structure as a young phenomenon: hints from its member satellites
• The satellite galaxy plane of NGC 4490 in light of ΛCDM - Sparsity of similarly extreme analogs and a possible role of satellite pairs
• The LMC impact on the kinematics of the Milky Way satellites: clues from the running solar apex
• Satellite group infall into the Milky Way: exploring the Crater-Leo case with new HST proper motions
• The Magellanic Clouds are very rare in the IllustrisTNG simulations
• Investigating the Dark Matter Halo of NGC 5128 using a Discrete Dynamical Model
• Testing a proposed "planarity" tool for studying satellite systems: On the alleged consistency of Milky Way satellite galaxy planes with $\Lambda$CDM
• The long-term stability of the Vast Polar Structure and its connection to a possible previous passage of the LMC