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It’s time for some plane speaking

The Milky Way, Andromeda and Centaurus A host flattened arrangements of satellite dwarf galaxies with correlated kinematics. The rarity of similar structures in cosmological simulations constitutes a major problem for the ΛCDM model, with no obvious solution in sight.

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Fig. 1: Planes of satellite galaxies are best studied for three nearby systems.
Fig. 2: Measurement uncertainties decrease the degree of measured correlation, with the consequence of artificially inflating the frequency of similarly extreme analogues in simulations.


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I thank B. Famaey, G. Lewis, F. Lelli, S. McGaugh and O. Müller for helpful comments. This work was supported by Leibniz-Junior Research Group grant J94/2020 via the Leibniz Competition, and a Klaus Tschira Boost Fund provided by the Klaus Tschira Stiftung and the German Scholars Organization.

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Correspondence to Marcel S. Pawlowski.

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Pawlowski, M.S. It’s time for some plane speaking. Nat Astron 5, 1185–1187 (2021).

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