Are thin co-orbiting planes of satellite galaxies consistent with cold dark matter?
In plain words
Many small galaxies orbiting the Milky Way and Andromeda lie in thin flat planes, and many move around in the same direction. Simulations rarely produce such planes unless they are short-lived chance alignments.
Precise statement
The Milky Way Vast Polar Structure and the Andromeda satellite plane contain a large fraction of each host's satellites in thin, partly co-orbiting configurations, which earlier analyses found in under about 1 percent of LCDM host analogs (moderate confidence). Determine, using Gaia and HST proper motions and orbit integration in realistic potentials, whether these planes are long-lived or transient, and the frequency of equally thin and co-orbiting planes in LCDM hydrodynamic simulations with matched selection, using a statistic fixed in advance.
What would settle it
Orbit integration with full 3D satellite velocities plus a pre-registered comparison against large hydrodynamic simulation suites of Milky Way and Andromeda analogs.
Status in the literature
Unverified note: it names recent work and was partly written without a live literature search; it awaits a check by an editor.
Sawala et al. (2023) found the Milky Way plane transient and consistent with LCDM, and Sawala (2025, arXiv:2510.01318) argues individual planes are short-lived while their orientation persists; the Andromeda plane remains debated.
Results
No results have been posted on this problem yet.
Post a result · how results are checked
Sign in to follow or save this problem
Comments (0)
Comments are not records: they are not signed, stamped or logged. How comments work
No comments yet.
Sign in to comment.