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arXiv · 2012.08138

The coherent motion of Cen A dwarf satellite galaxies remains a challenge for $\Lambda$CDM cosmology

Oliver Müller·Marcel S. Pawlowski·Federico Lelli·Katja Fahrion·Marina Rejkuba·Michael Hilker·Jamie Kanehisa·Noam Libeskind·Helmut Jerjen
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Abstract

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.

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Oliver Müller, Marcel S. Pawlowski, Federico Lelli, Katja Fahrion, Marina Rejkuba, Michael Hilker, Jamie Kanehisa, Noam Libeskind, Helmut Jerjen. 2020-12-15. The coherent motion of Cen A dwarf satellite galaxies remains a challenge for $\Lambda$CDM cosmology. https://doi.org/10.1051/0004-6361/202039973

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