Presentation #209.08 in the session Cosmology I.
Recent observations have found that satellite galaxies orbiting local galaxies tend to align their orbits in one or two thin planes around the host galaxy. This has been observed in Andromeda, Centaurus A, and our own Milky Way. Numerical simulations in a cosmological context (assuming a Lambda Cold Dark Matter, LCDM, model of cosmology) find these planes are either rare, occurring in less than 2% of Milky Way type systems, or short-lived. This is inconsistent with observations because of their apparent ubiquity in our local Universe. We believe inflow along filaments of the cosmic web is the main driver of evolution of these planar alignments, a dependence that past studies did not fully explore, and find planes of satellites in about 30% of Milky Way mass galaxies in our simulation. Specifically, we use the high precision, hydrodynamic, cosmological zoom simulation, New Horizon, which has a large enough volume to simulate the cosmic web, (16 Mpc)3, and high enough resolution to simulate dwarf galaxies (~ 35 pc). In addition, we demonstrate that the identified planes are statistically incompatible with a spherically isotropic distribution, or one that traces the shape of the dark matter halo. Furthermore, many planes in our simulation (about ~ 60%) also display strong signs of co-rotation, similar to those seen in observations. Given these results, it seems possible that the ubiquity of planes observed in our local Universe is in agreement with our simulations, and therefore LCDM.