Butterfly in a Cocoon, Understanding the Origin and Morphology of Globular Cluster Streams: The Case of GD-1
Abstract
Tidally disrupted globular cluster (GC) streams are usually observed, and therefore perceived, as narrow, linear, and one-dimensional structures in the 6D phase space. Here, we show that the GD-1 stellar stream, which is the tidal debris of a disrupted GC, possesses a secondary diffuse and extended stellar component (∼100 pc wide) around it, detected at the >5σ confidence level. Similar morphological properties are seen in synthetic streams that are produced from star clusters that are formed within dark matter sub-halos and then accrete onto a massive host galaxy. This lends credence to the idea that the progenitor of the highly retrograde GD-1 stream was originally formed outside of the Milky Way in a now defunct dark satellite galaxy. We deem that in future studies, this newly found cocoon component may serve as a structural hallmark to distinguish between the in situ and ex situ (accreted) formed GC streams.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2019
- DOI:
- 10.3847/1538-4357/ab2e07
- arXiv:
- arXiv:1903.08141
- Bibcode:
- 2019ApJ...881..106M
- Keywords:
-
- Galaxy: formation;
- Galaxy: halo;
- Galaxy: structure;
- globular clusters: general;
- stars: kinematics and dynamics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 11 pages, 10 figures, accepted for publication in The Astrophysical Journal