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arXiv 2209.03237astro-ph.GA
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NGC 346的内部视线运动学:核心区域的旋转

The internal line-of-sight kinematics of NGC 346: the rotation of the core region

Peter Zeidler, Elena Sabbi, Antonella Nota

摘要:

本文对年轻的大质量小麦哲伦星云星团NGC 346的中心1x 1 '进行了恒星径向速度分析。使用VLT/MUSE积分场光谱结合哈勃空间望远镜测光,我们提取103光谱的集群成员恒星适合测量准确的视线运动学。相对于系统速度165.5+/-0.2 km/s,星团成员星显示出v1 = -3.3(+0.3/-0.2)km/s和v2 = 2.6(+0.1/-0.1)km/s两个不同的速度群,并暗示第三个速度群v3 = 9.4(+0.1/-0.1 km/s。我们发现,既没有速度组和恒星的空间位置之间的相关性,也没有他们的轨迹上的光学色-星等图,这使得恒星速度的一个关键参数,以分离在这样一个年轻的星团中的单个恒星组件。速度组2显示出明显的自转,Ω 2 = -0.4 +/- 0.1 1/Myr,相当于-4.9+/-0.7 km/s,距离中心10 pc的径向距离,这可能是NGC 346通过巨大分子云的分级坍塌形成过程的残留物。电离气体已经失去了任何出生的运动学印记,并显示出明显的膨胀,由远紫外线通量和星团中心众多OB星的恒星风驱动。这个膨胀气泡的大小和7.9公里/秒的膨胀速度与最近的恒星形成事件发生在大约200万年前的估计非常一致。

英文摘要:

We present the stellar radial velocity analysis of the central 1x1' of the young massive Small Magellanic Cloud star cluster NGC 346. Using VLT/MUSE integral field spectroscopy in combination with Hubble Space Telescope photometry we extract 103 spectra of cluster member stars suited to measure accurate line-of-sight kinematics. The cluster member stars show two distinct velocity groups at v1 = -3.3 (+0.3/-0.2) km/s and v2 = 2.6 (+0.1/-0.1) km/s, relative to the systemic velocity of 165.5+/-0.2 km/s, and hint for a third group at v3 = 9.4 (+0.1/-0.1 km/s. We show that there is neither a correlation between the velocity groups and the spatial location of the stars, nor their locus on optical color-magnitude diagrams, which makes the stellar velocity a key parameter to separate individual stellar components in such a young star cluster. Velocity group 2 shows clear rotation with Omega2 = -0.4 +/- 0.1 1/Myr, corresponding to -4.9+/-0.7 km/s at radial distance of 10 pc from the center, a possible remnant of the formation process of NGC 346 through the hierarchical collapse of the giant molecular cloud. The ionizing gas has lost any natal kinematic imprint and shows clear expansion, driven by far ultra violet fluxes and stellar winds of the numerous OB stars in the cluster center. The size of this expanding bubble and its expansion velocity of 7.9 km/s is in excellent agreement with the estimate that the latest star formation episode occurred about two million years ago.

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