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The coherent motion of Cen A dwarf satellite galaxies remains a challenge for ΛCDM cosmology

Müller, Oliver, Pawlowski, Marcel S., Lelli, Federico, Fahrion, Katja, Rejkuba, Marina, Hilker, Michael, Kanehisa, Jamie, Libeskind, Noam and Jerjen, Helmut 2021. The coherent motion of Cen A dwarf satellite galaxies remains a challenge for ΛCDM cosmology. Astronomy and Astrophysics 645 , L5. 10.1051/0004-6361/202039973

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The plane-of-satellites problem is one of the most severe small-scale challenges for the standard Λ cold dark matter (ΛCDM) 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 that 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 they 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 ΛCDM, which is largely independent from baryon physics.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Additional Information: Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (
Publisher: EDP Sciences
ISSN: 0004-6361
Date of First Compliant Deposit: 28 July 2021
Date of Acceptance: 14 December 2020
Last Modified: 30 May 2023 02:41

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