Serendipitous Discovery of a Thin Stellar Stream near the Galactic Bulge in the Pan-STARRS1 3Pi Survey

TL;DR

A new, nearby, thin stellar stream was discovered near the Galactic bulge using Pan-STARRS1 data, revealing potential for more such discoveries in dense Galactic regions.

Contribution

This paper reports the first discovery of a thin stellar stream near the Galactic bulge, identified through Pan-STARRS1 photometry, with detailed characterization suggesting a globular cluster origin.

Findings

Stream is 2.5° long and 6' wide, with a blue horizontal-branch.

Population is old and metal-poor, at ~9.5 kpc distance.

Progenitor likely a globular cluster.

Abstract

We report the discovery of a thin stellar stream found in Pan-STARRS1 photometry near the Galactic bulge in the constellation of Ophiuchus. It appears as a coherent structure in the colour-selected stellar density maps produced to search for tidal debris around nearby globular clusters. The stream is exceptionally short and narrow; it is about 2.5{\deg} long and 6' wide in projection. The colour-magnitude diagram of this object, which harbours a blue horizontal-branch, is consistent with an old and relatively metal-poor population ([Fe/H]~-1.3) located 9.5 +/- 0.9 kpc away at (l,b) ~ (5{\deg},+32{\deg}), and 5.0 +/- 1.0 kpc from the Galactic centre. These properties argue for a globular cluster as progenitor. The finding of such a prominent, nearby stream suggests that many streams could await discovery in the more densely populated regions of our Galaxy.