The Young Massive Star Cluster Westerlund 2 Observed with MUSE. I. First Results on the Cluster Internal Motion from Stellar Radial Velocities
The Young Massive Star Cluster Westerlund 2 Observed with MUSE. I. First Results on the Cluster Internal Motion from Stellar Radial Velocities
复制标题
DOI：
10.3847/1538-3881/aae258
复制
发表时间：
2018-09
期刊：
影响因子：
--
通讯作者：
P. Zeidler;E. Sabbi;A. Nota;A. Pasquali;E. Grebel;A. McLeod;S. Kamann;M. Tosi;M. Cignoni
中科院分区：
文献类型：
--
作者：
P. Zeidler;E. Sabbi;A. Nota;A. Pasquali;E. Grebel;A. McLeod;S. Kamann;M. Tosi;M. Cignoni
韦斯特伦德2（Westerlund 2，Wd 2）是H ii区RCW 49的中心电离星星团，也是银河系中质量第二大的年轻星星团。它的年龄很小（2000万年），距离太阳很近（2400万秒差距），这使它成为研究从母气云中出现的恒星、大量的OB星及其对气体的反馈以及气体动力学的理想目标。我们结合联合收割机的高分辨率多波段测光获得的光学和近红外与哈勃太空望远镜，甚大望远镜/MUSE积分场光谱研究的气体，恒星，以及它们之间的相互作用，同时。在这篇论文中，我们关注的是主星团中心以北的一个64 × 64 arcsec 2的小区域，我们称之为北方气泡（NB），它是一个刻在星团区域气体中的圆形空腔。利用MUSE数据，我们确定了NB中从G9 III到O7.5的17颗恒星的光谱类型。通过对这些光谱类型的估计，我们在先前公布的Wd 2中37颗OB星的普查中增加了2颗O型星和5颗B型星。为了测量径向速度，我们提取了整个Wd 2的72个恒星光谱，包括NB的17个，并表明星团成员恒星遵循以大约为中心的双峰速度分布。（8.10 ± 1.53）km s-1和（25.41 ± 1.57）km s-1，色散分别为（4.52 ± 1.78）km s-1和（3.46 ± 1.29）km s-1。这些都与CO（J = 1-2）的研究RCW 49离开云-云碰撞作为一个可行的选择的形成方案的Wd 2。在盖亚DR 2自行中也检测到双峰分布。
Westerlund 2 (Wd2) is the central ionizing star cluster of the H ii region RCW 49 and the second most massive young star cluster ( ) in the Milky Way. Its young age (∼2 Myr) and close proximity to the Sun (∼4 kpc) 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 × 64 arcsec2 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) km s−1 and (25.41 ± 1.57) km s−1 with a dispersion of (4.52 ± 1.78) km s−1 and (3.46 ± 1.29) km s−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.