论文标题
缪斯群的光谱观察结果
MUSE spectroscopic observations of the Young Massive Cluster NGC1850
论文作者
论文摘要
NGC1850是当地群中最近的年轻大型群集，其质量与银河球状簇相似。最近的研究表明，其MSTO的形态扩展，可以将其解释为年龄或内部旋转的扩散。精确的光谱测定其化学特性仍然缺失。我们分析了该群集的两个组件（NGC1850A和NGC1850B）的1167颗恒星自适应光学模式获得的光谱。多亏了此数据集，我们测量的平均金属度为<[m/h]> = -0.31 +/- 0.01，平均BA丰度为<[ba/fe]> = +0.40 +/- 0.02和<v_ {los}> = 251.1 +/-- 0.3 km/s/s的全身性radial速度。径向速度的分散液表明，动态质量（m/ms）= 4.84 +/- 0.1，而未检测到明显的全身旋转。我们检测到NGC1850a的TO恒星中OI线强度的显着双峰性，其中约66％的恒星具有[O/Fe]〜-0.16，其余的则无可检测线。大多数O-Weak星星优先填充了MSTO的红色侧并在发射中显示H线，这表明它们是恒星，旋转接近其临界速度。在正常的MSTO恒星中，红色恒星的平均宽线轮廓比蓝色的恒星具有比蓝色的曲线更宽，这表明颜色与旋转速度之间存在相关性。该簇的平均金属性位于LMC年龄金属关系后LMC金属性分布的金属富金属侧。 BA和O的丰度与该星系标准中测得的那些一致。观察到的在其MS恒星中的OI线宽度的扩散可以解释为O-Weak恒星信封中发生的旋转混合的效果。线扩展与颜色之间的相关性表明，观察到的颜色在关闭恒星之间扩散可能是由于这些恒星覆盖的旋转速度范围很大。
NGC1850 is the nearest Young Massive Cluster of the Local Group with a mass similar to those of Galactic globular clusters. Recent studies have revealed an extended morphology of its MSTO, which can be interpreted as a spread in either age or internal rotation. An accurate spectroscopic determination of its chemical properties is still missing. We analyse spectra obtained with MUSE in adaptive optics mode of 1167 stars in both components of this cluster (NGC1850A and NGC1850B). Thanks to this dataset, we measure an average metallicity of <[M/H]>=-0.31 +/- 0.01, a mean Ba abundance of <[Ba/Fe]>=+0.40 +/- 0.02 and a systemic radial velocity of <v_{LOS}>=251.1 +/- 0.3 km/s. The dispersion of the radial velocities suggests a dynamical mass of log(M/Ms)=4.84 +/- 0.1, while no significant systemic rotation is detected. We detect a significant bimodality in OI line strength among the TO stars of NGC1850A with ~66% of stars with [O/Fe]~-0.16 and the rest with no detectable line. The majority of O-weak stars populate preferentially the red side of the MSTO and show H lines in emission, suggesting that they are Be stars rotating close to their critical velocity. Among normal MSTO stars, red stars have on average broader line profiles than blue ones, suggesting a correlation between colour and rotational velocity. The mean metallicity of this cluster lies at the metal-rich side of the metallicity distribution of the LMC following its age-metallicity relation. The Ba and O abundances agree with those measured in the bar of this galaxy. The observed spread in OI line width among its MS stars can be interpreted as an effect of rotational mixing occurring in the envelopes of O-weak stars. The correlation between line broadening and colour suggests that the observed colour spread among turn-off stars can be due to a wide range in rotational velocity covered by these stars.
