Exploring the Metal-Poor Stream C-19: A Glimpse into Galactic Formation

The study delves into the C-19 stellar stream, the most metal-poor known, potentially originating from a disrupted globular cluster (GC) or a dwarf galaxy. Researchers, led by P. Bonifacio, used advanced spectroscopic observations of subgiant stars to clarify C-19's chemical and dynamical properties.

Key Findings and Methods

C-19's stars exhibit extremely low metallicity ([Fe/H] = -3.1), implying formation from metal-poor gas. Researchers employed the X-shooter spectrograph to observe 15 stars, measuring radial velocities and chemical abundances. Using likelihood modeling, 12 stars were confirmed as C-19 members, while 3 were contaminants. This reinforced earlier findings of uniform metallicity and velocity dispersion within the stream.

Debate on Origins

While C-19's properties align with a GC origin, its width and velocity dispersion suggest a potential dwarf galaxy progenitor. The spread in magnesium abundances adds complexity, hinting at a massive origin similar to known clusters like NGC 4833.

Implications for Galactic Evolution

This study challenges existing theories of globular cluster formation by pushing the metallicity boundary and exploring the role of dark matter in stellar stream dynamics. Whether C-19 arose from a GC or a dwarf galaxy remains open, but its extreme properties offer vital clues to early galactic structures.

Conclusion

C-19 serves as a window into the early universe, requiring further study to untangle its enigmatic past. The team's work underscores the complexity of tracing galactic history through stellar archaeology.

Source: Bonifacio