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

TL;DR

This study uses deep photometric data to analyze the GD-1 stellar stream, revealing detailed density variations, potential progenitor location, and signs of past interactions with the Milky Way's disk or sub-halos.

Contribution

It provides the first high-quality photometric analysis of GD-1's morphology and density, identifying density variations and a candidate progenitor location.

Findings

Detected density variations and stream fanning.

Identified a potential progenitor candidate at a density under-density.

Evidence of disturbances from interactions with the Milky Way or sub-halos.

Abstract

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. We also detect a clear under-density in the middle of the stream track at $\varphi_{1}$=-45 deg surrounded by overdense stream segments on either side. This location is a promising candidate for the elusive missing progenitor of the GD-1 stream. We conclude that the GD-1 stream has clearly been disturbed by interactions with the Milky Way disk or other sub-halos.