Origin of the outer stellar population of Boötes I

Determine whether the outer stellar population of the Milky Way ultra-faint dwarf galaxy Boötes I was produced primarily by tidal stripping during interaction with the Milky Way or by the merger of Boötes I with a separate low-mass dwarf galaxy.

Background

Boötes I exhibits an extended outer stellar distribution whose morphology is consistent with tidal features aligned with its Galactic orbit. However, the paper also notes that the chemical similarity of some outer metal-poor stars could indicate that they formed in a separate low-mass dwarf galaxy that later merged with Boötes I. Consequently, the physical origin of the outer population remains unresolved between tidal stripping and a past dwarf–dwarf merger.