Mon. Not. R. Astron. Soc., 473, 3325-3350 (2018)
SiO maser survey towards off-plane O-rich AGBs around the orbital plane of the Sagittarius stellar stream.
WU Y.W., MATSUNAGA N., BURNS R.A. and ZHANG B.
Abstract (from CDS):
We conducted an SiO maser survey towards 221 O-rich AGB stars, with the aim of identifying maser emission associated with the Sagittarius stellar stream. In this survey, maser emission was detected in 44 targets, of which 35 were new detections. All of these masers are within 5 kpc of the Sun. We also compiled a Galactic SiO maser catalogue including ∼2300 SiO masers from the literature. The distribution of these SiO masers gives a scaleheight of 0.40 kpc, while 42 sources deviate from the Galactic plane by more than 1.2 kpc, half of which were found in this survey. Regarding SiO masers in the disc, we found that both rotational speeds and velocity dispersions vary with Galactic plane distance. Assuming a Galactic rotational speed Θ0 = 240 km s–1, we derived velocity lags of 15 and 55 km s–1 for disc and off-plane SiO masers, respectively. Moreover, we identified three groups with significant peculiar motions (with 70 per cent confidence). The most significant group is in the thick disc that might trace stream/peculiar motion of the Perseus arm. The other two groups are mainly made up of off-plane sources. The northern and southern off-plane sources were found to be moving at ∼ 33 and 54 km s–1 respectively away from the Galactic plane. The causes of these peculiar motions are still unclear. For the two off-plane groups, we suspect that they are thick disc stars, with kinematics affected by the Sgr stellar stream or very old Sgr stream debris.
© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
masers - stars: AGB and post-AGB - Galaxy: structure - radio lines: stars
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