Multiple components of the Jhelum stellar stream

Understand

In simple models of the Milky Way, tidally disrupting satellites produce long and thin---nearly one-dimensional---stellar streams.

• Using astrometric data from the Gaia second data release and photometry from the Dark Energy Survey, we demonstrate that the Jhelum stream, a stellar stream in the inner halo, is a two-dimensional structure.
• The spatial distribution of highly probable Jhelum members reveals a dense thin component and an associated diffuse, spatially offset component.
• These two spatial components have indistinguishable proper motions (at $\sigma\sim1\,\rm mas\,yr^{-1}$ level) and a similar ratio of blue straggler to blue horizontal branch stars, which indicates a common origin for the two components.