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标题：The Young Massive Star Cluster Westerlund 2 Observed with MUSE. I. First Results on the Cluster Internal Motion from Stellar Radial Velocities
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作者：Peter Zeidler ; Elena Sabbi ; Antonella Nota 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2018
卷号：156
期号：5
页码：1-15
DOI：10.3847/1538-3881/aae258
语种：English
出版社：American Institute of Physics
摘要：Westerlund 2 (Wd2) is the central ionizing star cluster of the H II region RCW49 and the second most massive young star cluster ( = ( ) M M 3.6 0.3 10 4 ) in the Milky Way. Its young age (∼2Myr) and close proximity to the Sun (∼4kpc) makes it a perfect target to study stars emerging from their parental gas cloud, the large number of OB-stars and their feedback onto the gas, and the gas dynamics. We combine high-resolution multi-band photometry obtained in the optical and near-infrared with the Hubble Space Telescope, and Very Large Telescope/MUSE integral field spectroscopy to study the gas, the stars, and their interactions, simultaneously. In this paper we focus on a small, 64×64arcsec 2 region north of the main cluster center, which we call the Northern Bubble (NB), a circular cavity carved into the gas of the cluster region. Using MUSE data, we determined the spectral types of 17 stars in the NB from G9III to O7.5. With the estimation of these spectral types, we add 2 O and 5 B-type stars to the previously published census of 37 OB-stars in Wd2. To measure radial velocities we extracted 72 stellar spectra throughout Wd2, including the 17 of the NB, and show that the cluster-member stars follow a bimodal velocity distribution centered around (8.10±1.53)kms −1 and (25.41±1.57)kms −1 with a dispersion of (4.52±1.78)kms −1 and (3.46±1.29)kms −1 , respectively. These are in agreement with CO(J=1–2) studies of RCW49 leaving cloud–cloud collision as a viable option for the formation scenario of Wd2. The bimodal distribution is also detected in the Gaia DR2 proper motions.
关键词：Galaxy: kinematics and dynamics;Galaxy: open clusters and associations: individual (Westerlund 2);H II regions;stars: early-type;techniques: radial velocities