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Using ESA's Gaia satellite, astronomers have detected 87 stellar streams associated with globular clusters (GCs) in our Milky Way galaxy. The discovery, which doubles the number of known GC stellar streams, was detailed in a research paper October 16 on the arXiv pre-print server.

Stellar streams are remnants of dwarf galaxies or globular clusters that once orbited a galaxy but have been disrupted and stretched out along their orbits by tidal forces of their hosts. Observations show that many stellar streams are elongated debris of tidally disrupted globular clusters.

Finding new galactic stellar streams, including the ones that are remnants of GCs, and investigating them could answer some crucial questions about the galaxy. For instance, stellar streams could help us understand the large-scale mass distribution of the galactic dark matter halo. Moreover, they could confirm whether or not our galaxy contains low-mass dark matter subhalos.

Now, a team of astronomers led by Yingtian Chen of the University of Michigan reports the detection of nearly a hundred GC stellar streams. Their discovery is a result of employing the automatic stellar stream detection algorithm named "StarStream."

"The high detection quality makes StarStream a powerful tool to uncover GC streams that may have been missed by previous methods," the researchers explain.

All in all, the list of GC stellar streams revealed by Chen's team contains a high-quality sample of 34 streams within the 10 degree search radius, and a low-quality sample of 53 streams with higher extinction or background density. The researchers underlined that their detection significantly improves our knowledge of GC streams, as even just the high-quality sample doubles the number of known GC streams to date.

Furthermore, the astronomers measured the orbit-averaged mass loss rate of the progenitor GCs of the identified streams. It turned out that most of these GCs have this rate at a level between 1.0 and 100 solar masses per one million years. The study did not find any strong correlation between the mass loss rate and other properties of the globular clusters.

The observations found that many new stellar streams are wide or short, or misaligned with their progenitors' orbits. For instance, the stream of NGC 4147 is almost a circular blob. This contradicts the visual expectation that streams are thin features elongated along the progenitor's orbit.

"The detection of these 'irregular' or misaligned streams highlights the power of the physics-based modeling of GC streams by StarStream. As many GC streams can be dynamically hot or spatially complex depending on the GC's mass and orbit, these streams are likely missed by traditional visually-based methods," the authors of the paper conclude.

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