通过暗能量光谱仪器对矮星系武仙座的恒星二元分数进行研究
The Binary Fraction of Stars in the Dwarf Galaxy Ursa Minor via Dark Energy Spectroscopic Instrument
AI总结：
通过暗能量光谱仪器研究武仙座矮星系成员恒星的二元分数，发现金属含量较高群体的二元分数略高，且中心集中群体的二元分数较低。
摘要：
我们利用暗能量光谱仪器的银河系暗能量巡天提供的多 epoch 目标径向速度测量数据，来估计成员恒星在矮椭圆星系武仙座的二元分数。我们的数据集包含670个不同的成员恒星，总计超过2000次观测，收集于大约一年时间。我们约束武仙座的二元分数为$0.61^{+0.16}_{-0.20}$和$0.69^{+0.19}_{-0.17}$，分别基于太阳邻近观测的Duquennoy & Mayor (1991)和Moe & Di Stefano (2017)的二元轨道参数分布。此外，通过将我们的数据分成两个子样本，以中位数金属含量为界，我们发现金属含量较高的([Fe/H]>-2.14)群体的二元分数略高于金属含量较低([Fe/H]<-2.14)群体。基于Moe & Di Stefano模型，武仙座中金属含量较高和较低群体的最佳约束二元分数分别为$0.86^{+0.14}_{-0.24}$和$0.48^{+0.26}_{-0.19}$。经过彻底检查，我们发现这种偏移不能归因于样本选择效应。我们还根据其投影半径到武仙座中心将数据分成两个子样本，并发现更集中在密集环境中的群体具有较低的二元分数$0.33^{+0.30}_{-0.20}$，与更外围子样本的$1.00^{+0.00}_{-0.32}$相比。
英文摘要：
We utilize multi-epoch line-of-sight velocity measurements from the Milky Way Survey of the Dark Energy Spectroscopic Instrument to estimate the binary fraction for member stars in the dwarf spheroidal galaxy Ursa Minor. Our dataset comprises 670 distinct member stars, with a total of more than 2,000 observations collected over approximately one year. We constrain the binary fraction for UMi to be $0.61^{+0.16}_{-0.20}$ and $0.69^{+0.19}_{-0.17}$, with the binary orbital parameter distributions based on solar neighborhood observation from Duquennoy & Mayor (1991) and Moe & Di Stefano (2017), respectively. Furthermore, by dividing our data into two subsamples at the median metallicity, we identify that the binary fraction for the metal-rich ([Fe/H]>-2.14) population is slightly higher than that of the metal-poor ([Fe/H]<-2.14) population. Based on the Moe & Di Stefano model, the best-constrained binary fractions for metal-rich and metal-poor populations in UMi are $0.86^{+0.14}_{-0.24}$ and $0.48^{+0.26}_{-0.19}$, respectively. After a thorough examination, we find that this offset cannot be attributed to sample selection effects. We also divide our data into two subsamples according to their projected radius to the center of UMi, and find that the more centrally concentrated population in a denser environment has a lower binary fraction of $0.33^{+0.30}_{-0.20}$, compared with $1.00^{+0.00}_{-0.32}$ for the subsample in more outskirts.
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