At a Crossroads: Stellar Streams in the South Galactic Cap

TL;DR

This paper identifies and characterizes four new stellar stream candidates in the South Galactic Cap using PanSTARRs data, revealing their properties, possible origins, and relation to known streams.

Contribution

It reports the discovery and detailed analysis of four new stellar streams, including their trajectories, sizes, and potential progenitors, expanding knowledge of Galactic structure.

Findings

Four new stellar stream candidates identified near the south Galactic pole.

Streams are approximately 20 kpc away, 13-95 degrees long, and 100-300 pc wide.

Streams suggest progenitors similar to globular clusters and possible common origins with known streams.

Abstract

We examine the distribution of old, metal-poor stars in a portion of the recently released PanSTARRs survey. We find an interesting confluence of four new cold stellar stream candidates that appear to converge on or pass near the south Galactic pole. The stream candidates, which we designate Murrumbidgee, Molonglo, Orinoco, and Kwando, lie at a distance of approximately 20 kpc and range in length from 13 to 95 degrees, or about 5 to 33 kpc. The stream candidates are between 100 and 300 pc in width, and are estimated to contain between 3000 and 8000 stars each, suggesting progenitors similar to modern day globular clusters. The trajectories of the streams imply orbits that range from hyperbolic to nearly circular. The Molonglo stream is nearly parallel to, at the same distance as, and offset by only 2.5 degrees from the previously discovered ATLAS stream, suggesting a possible common origin. Orinoco and Kwando also have similarly shaped, moderately eccentric, obliquely viewed orbits that suggest distinct progenitors within a common, larger parent body.