A deeper look at the GD1 stream: density variations and wiggles

Understand

Using deep photometric data from CFHT/Megacam, we study the morphology and density of the GD-1 stream, one of the longest and coldest stellar streams in the Milky Way.

• Our deep data recovers the lower main sequence of the stream with unprecedented quality, clearly separating it from Milky Way foreground and background stars.
• An analysis of the distance to different parts of the stream shows that GD-1 lies at a heliocentric distance between 8 and 10 kpc, with only a shallow gradient across 45 deg on the sky.
• Matched filter maps of the stream density show clear density variations, such as deviations from a single orbital track and tentative evidence for stream fanning.