A whirling plane of satellite galaxies around Centaurus A challenges cold dark matter cosmology

TL;DR

This paper presents evidence of a co-rotating plane of satellite galaxies around Centaurus A, which is rare in standard cosmological simulations, challenging current models of galaxy formation.

Contribution

It provides the first observational evidence of a coherent, corotating satellite plane around Centaurus A, questioning the rarity predicted by cosmological simulations.

Findings

14 out of 16 satellites follow a coherent velocity pattern

Less than 0.5% of similar systems in simulations show this behavior

Corotating satellite systems may be more common than previously thought

Abstract

The Milky Way and Andromeda galaxy are each surrounded by a thin plane of satellite galaxies that may be corotating. Cosmological simulations predict that most satellite galaxy systems are close to isotropic with random motions, so those two well-studied systems are often interpreted as rare statistical outliers. We test this assumption using the kinematics of satellite galaxies around the Centaurus A galaxy. Our statistical analysis reveals evidence for corotation in a narrow plane: of the 16 Centaurus A's satellites with kinematic data, 14 follow a coherent velocity pattern aligned with the long axis of their spatial distribution. In standard cosmology simulations, < 0.5% of Centaurus A-like systems show such behavior. Corotating satellite systems may be common in the Universe, challenging small-scale structure formation in the prevailing cosmological paradigm.