At a Crossroads: Stellar Streams in the South Galactic Cap

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.

9 pages, 4 figures, accepted for publication in the Astrophysical Journal, final version

References in corpus (9)

• The Gaia mission
• Detection of a 63 Degree Cold Stellar Stream in the Sloan Digital Sky Survey
• Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5
• The shape of the inner Milky Way halo from observations of the Pal 5 and GD-1 stellar streams
• A Synoptic Map of Halo Substructures from the Pan-STARRS1 3π Survey
• The mechanics of tidal streams
• Discovery of a cold stellar stream in the ATLAS DR1 data
• The Complex Structure of Stars in the Outer Galactic Disk as revealed by Pan-STARRS1
• Fitting orbits to tidal streams with proper motions

Cited by in corpus (8)

• galstreams: A Library of Milky Way Stellar Stream Footprints and Tracks
• Orbital Clustering Identifies the Origins of Galactic Stellar Streams
• Fourteen candidate RR Lyrae star streams in the inner Galaxy
• Discovery of a new nearby globular cluster with extreme kinematics located in the extension of a halo stream
• Charting Galactic Accelerations with Stellar Streams and Machine Learning
• RR Lyrae stars as probes of the outer Galactic halo: Chemical and kinematic analysis of a pilot sample
• Gaps in stellar streams as a result of globular cluster fly-bys
• Very metal-poor stars in the solar vicinity: kinematics and abundance analysis