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arXiv · 1903.08141

Butterfly in a Cocoon, Understanding the origin and morphology of Globular Cluster Streams: The case of GD-1

Khyati Malhan·Rodrigo A. Ibata·Raymond G. Carlberg·Monica Valluri·Katherine Freese
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Abstract

Tidally disrupted globular cluster 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 ($\approx$ 30 pc wide), which is the tidal debris of a disrupted globular cluster, possesses a secondary diffuse and extended stellar component ($\approx$ 100 pc wide) around it, detected at >5$\sigma$ 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 globular cluster streams.

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Khyati Malhan, Rodrigo A. Ibata, Raymond G. Carlberg, Monica Valluri, Katherine Freese. 2019-03-19. Butterfly in a Cocoon, Understanding the origin and morphology of Globular Cluster Streams: The case of GD-1. https://doi.org/10.3847/1538-4357/ab2e07

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