The nature of the progenitor of the M31 north-western stream: globular clusters as milestones of its orbit
Approach
Test-particle trajectories use five candidate associated clusters as orbital constraints. Tidal-disruption arguments and N-body models test viable dwarf progenitors.
Main result
Two orbital branches remain, placing the stream in front of or behind M31. Both require pericentres larger than two kiloparsecs, and simulations reproduce basic stream features.
Scientific implications
A stream distance measurement can distinguish the branches, connecting imaging and spectroscopy to the satellite’s dynamical history.
Scope and limitations
The inference relies on cluster membership and the adopted M31 potential. This briefing describes the alternatives in the original paper, not a claim that they remain unresolved today.