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arXiv 1602.02702astro-ph.SRastro-ph.GA
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年轻大质量星系团NGC 2100中红超巨星的化学和运动学

Chemistry and Kinematics of Red Supergiant Stars in the Young Massive Cluster NGC 2100

L. R. Patrick, C. J. Evans, B. Davies, R-P. Kudritzki, V. Hénault-Brunet, N. Bastian, E. Lapenna, M. Bergemann

摘要:

利用K波段多目标摄谱仪(KMOS)对大麦云(LMC)中的年轻大质量星团NGC 2100中的14颗红超巨星(RSG)进行了近红外光谱观测。包括金属丰度在内的恒星参数是使用J波段分析技术估计的,该技术已在本地宇宙中进行了严格的测试。我们发现NGC 2100的平均金属丰度为[Z]= $-$ 0.43 $\pm$ 0.10 dex,与文献中对LMC的估计值非常一致。将我们在NGC 2100中的结果与具有类似质量和年龄的银河系星团(在太阳类金属丰度下)的结果进行比较,我们发现RSG在Hertzsprung-Russell图中的位置没有显着差异。我们结合所观察到的KMOS光谱,形成一个模拟的集成光团簇光谱,并表明,通过分析这个光谱作为一个单一的RSG,结果是一致的集群的平均属性。径向速度估计的目标和动力学性质估计的第一次在这个集群。这些数据与平坦的速度色散剖面一致,在95%的置信水平下,星团速度色散的上限为3.9公里/秒。然而,固有速度色散是未解决的,因此,可能会显着小于这里报告的上限。在维里平衡的假设下,得到了团簇动力学质量的上限为$M_{dyn}$ $\le$ $15.2\times10^{4}M_{\odot}$。

英文摘要:

We have obtained K-band Multi-Object Spectrograph (KMOS) near-IR spectroscopy for 14 red supergiant stars (RSGs) in the young massive star cluster NGC 2100 in the Large Magellanic Cloud (LMC). Stellar parameters including metallicity are estimated using the J-band analysis technique, which has been rigorously tested in the Local Universe. We find an average metallicity for NGC 2100 of [Z]=$-$0.43$\pm$0.10 dex, in good agreement with estimates from the literature for the LMC. Comparing our results in NGC 2100 with those for a Galactic cluster (at Solar-like metallicity) with a similar mass and age we find no significant difference in the location of RSGs in the Hertzsprung--Russell diagram. We combine the observed KMOS spectra to form a simulated integrated-light cluster spectrum and show that, by analysing this spectrum as a single RSG, the results are consistent with the average properties of the cluster. Radial velocities are estimated for the targets and the dynamical properties are estimated for the first time within this cluster. The data are consistent with a flat velocity dispersion profile, and with an upper limit of 3.9 km/s, at the 95% confidence level, for the velocity dispersion of the cluster. However, the intrinsic velocity dispersion is unresolved and could, therefore, be significantly smaller than the upper limit reported here. An upper limit on the dynamical mass of the cluster is derived as $M_{dyn}$ $\le$ $15.2\times10^{4}M_{\odot}$ assuming virial equilibrium.

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