论文标题
在2 Gyr Old old Cluster NGC 1846中对多个种群的高分辨率光谱搜索
A high-resolution spectroscopic search for multiple populations in the 2 Gyr old cluster NGC 1846
论文作者
论文摘要
我们提供了详细的C，O，Na，Mg，Si，Ca，Ti，V，Fe，Zr，Ba和Eu的丰度测量值，用于LMC星团NGC NGC 1846（[Fe/H] = -0.59）中的20个红色巨型分支（RGB）恒星。该簇为1.95 Gyr旧，位于假定的年龄限制（2 Gyr）以下，对于大型星团中有多个种群的存在。我们的测量基于高分辨率和低分辨率的VLT/火焰光谱，并结合了HST的光度数据。对于O，NA，MG，SI，CA，FE和BA，还包括非本地热力学平衡效应的校正。我们的结果表明，基于缺乏任何固有的星际到明星，在Na和o中没有任何固有的恒星到明星，我们没有证据表明多个人群：我们分别在$ \ leq 0.07 $和$ \ leq 0.09 $ dex的这些元素的固有分散体上对固有分散限制了95 \％的置信度限制。但是，我们确实检测到碳丰度的显着蔓延，表明在RGB上发生的进化混合发生了变化，随着光度的增加。总体而言，NGC 1846的一般丰度模式与以前对中级LMC星簇和现场恒星的研究相似。
We present detailed C, O, Na, Mg, Si, Ca, Ti, V, Fe, Zr, Ba, and Eu abundance measurements for 20 red giant branch (RGB) stars in the LMC star cluster NGC 1846 ([Fe/H] = -0.59). This cluster is 1.95 Gyr old and lies just below the supposed lower age limit (2 Gyr) for the presence of multiple populations in massive star clusters. Our measurements are based on high and low-resolution VLT/FLAMES spectra combined with photometric data from HST. Corrections for non-local thermodynamic equilibrium effects are also included for O, Na, Mg, Si, Ca, Fe and Ba. Our results show that there is no evidence for multiple populations in this cluster based on the lack of any intrinsic star-to-star spread in the abundances of Na and O: we place 95 \% confidence limits on the intrinsic dispersion for these elements of $\leq 0.07$ and $\leq 0.09$ dex, respectively. However, we do detect a significant spread in the carbon abundances, indicating varying evolutionary mixing occurring on the RGB that increases with luminosity. Overall, the general abundance patterns for NGC 1846 are similar to those seen in previous studies of intermediate-age LMC star clusters and field stars.
