Chemical compositions of stars in two stellar streams from the Galactic thick disk

TL;DR

This study analyzes the chemical compositions of stars in two stellar streams from the Galactic thick disk, revealing their old age, similar metallicity, and likely dynamical origin rather than being remnants of clusters or satellite debris.

Contribution

It provides detailed elemental abundances for stars in two streams, demonstrating their similarity to thick disk stars and suggesting a dynamical origin within the Galaxy.

Findings

Both streams are metal-poor and very old (10-14 Gyrs).

Streams' elemental abundances match those of local thick disk stars.

Streams are unlikely to be from dissolved clusters or accreted satellites.

Abstract

We present abundances for 20 elements for stars in two stellar streams identified by Arifyanto & Fuchs (2006, A&A, 449, 533): 18 stars from the Arcturus stream and 26 from a new stream, which we call AF06 stream, both from the Galactic thick disk. Results show both streams are metal-poor and very old (10$-$14 Gyrs) with kinematics and abundances overlapping with the properties of local field thick disk stars. Both streams exhibit a range in metallicity but with relative elemental abundances that are identical to those of thick disk stars of the same metallicity. These results show that neither stream can result from dissolution of an open cluster. It is highly unlikely that either stream represents tidal debris from an accreted satellite galaxy. Both streams most probably owe their origin to dynamical perturbations within the Galaxy.