Serendipitous discovery of a thin stellar stream near the Galactic bulge in the Pan-STARRS1 3π survey

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 long and 6 arcmin wide in projection. The colour-magnitude diagram of this object, which harbours a blue horizontalbranch, 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°, +32°), 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 themore densely populated regions of our Galaxy. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.