Water-maser survey towards off-plane O-rich AGBs around the orbital plane of the Sagittarius stellar stream

Abstract

ABSTRACT A 22 GHz water-maser survey was conducted towards 178 O-rich asymptotic giant branch (AGB) stars with the aim of identifying maser emission associated with the Sagittarius stellar stream. In this survey, maser emissions were detected in 21 targets, 20 of which were new detections. We studied the Galactic distributions of H2O- and SiO-maser-traced AGBs towards the Sgr orbital plane, and found an elongated structure towards the (l, b) ∼ (340°, 40°) direction. In order to verify its association with the Sagittarius tidal stream, we further studied the 3D motion of these sources, but found that, kinematically, these maser-traced AGBs are still Galactic disc sources rather than stream debris. In addition, we found a remarkable outward motion, ∼50 km s−1 away from the Galactic Centre of these maser-traced AGBs, but with no systermatic lag of rotational speed as reported in 2000 for solar-neighbourhood Miras.