The coherent motion of Cen A dwarf satellite galaxies remains a
  challenge for $\Lambda$CDM cosmology
  The plane-of-satellites problem is one of the most severe small-scale
challenges for the standard $\Lambda$CDM cosmological model: several dwarf
galaxies around the Milky Way and Andromeda co-orbit in thin, planar
structures. A similar case has been identified around the nearby elliptical
galaxy Centaurus A (Cen A). In this Letter, we study the satellite system of
Cen A adding twelve new galaxies with line-of-sight velocities from VLT/MUSE
observations. We find 21 out of 28 dwarf galaxies with measured velocities
share a coherent motion. Similarly flattened and coherently moving structures
are found only in 0.2% of Cen A analogs in the Illustris-TNG100 cosmological
simulation, independently of whether we use its dark-matter-only or
hydrodynamical run. These analogs are not co-orbiting, and arise only by chance
projection, thus they are short-lived structures in such simulations. Our
findings indicate that the observed co-rotating planes of satellites are a
persistent challenge for $\Lambda$CDM, which is largely independent from baryon
physics.
