$χ^{1}$天炉座星团DANCe。用Gaia-EDR3普查星团的恒星、结构和运动学
$χ^{1}$ Fornacis cluster DANCe. Census of stars, structure, and kinematics of the cluster with Gaia-EDR3
摘要：
内容：$χ^{1}$天炉座星团（Alessi 13）是太阳附近为数不多的几个年龄和距离的疏散星团之一，应该得到更多的关注，因为它可以作为未来许多与恒星和行星形成有关的研究的基石。目的：我们利用盖亚太空任务第三次数据发布的早期安装，结合档案数据和我们自己的观察，扩大集群成员的普查，并重新审视集群的一些属性。研究方法：我们应用概率的方法来推断成员的概率超过1000度${^2}$的字段选择最有可能的集群成员，并得出的距离，空间速度和物理性质的恒星在这个样本。结果：我们确定了164个高概率的集群成员（包括61个新成员），涵盖了5.1至19.6等的G带星等范围。我们的集群成员的样本是完整的0.04 M $_{\odot}$。我们从贝叶斯推断中推导出了$108.4\pm0.3$ pc的距离，并证实了该星团与杜鹃座-时钟座、天鸽座和船底座年轻恒星协同运动。我们调查的运动学的集群从一个子样本的恒星测量径向速度，我们没有发现任何显着的膨胀或旋转的集群的影响。我们的研究结果表明，集群是有点年轻（约30万年）比以前认为的。基于光谱观测，我们认为，集群是质量分离和光谱类型的分布相比，其他年轻的恒星群显示出很小的变化。结论：在这项研究中，我们提供了最完整的集群成员普查，可以单独使用盖亚数据完成，我们使用这个新的样本来提供集群6D结构的更新图片。
英文摘要：
Context: The $χ^{1}$ Fornacis cluster (Alessi 13) is one of a few open clusters of its age and distance in the Solar neighbourhood that ought to benefit from more attention as it can serve as a cornerstone for numerous future studies related to star and planet formation. Aims: We take advantage of the early installment of the third data release of the Gaia space mission in combination with archival data and our own observations, to expand the census of cluster members and revisit some properties of the cluster. Methods: We applied a probabilistic method to infer membership probabilities over a field of more than 1000 deg${^2}$ to select the most likely cluster members and derive the distances, spatial velocities, and physical properties of the stars in this sample. Results: We identify 164 high-probability cluster members (including 61 new members) covering the magnitude range from 5.1 to 19.6 mag in the G-band. Our sample of cluster members is complete down to 0.04 M$_{\odot}$. We derive the distance of $108.4\pm0.3$ pc from Bayesian inference and confirm that the cluster is comoving with the Tucana-Horologium, Columba, and Carina young stellar associations. We investigate the kinematics of the cluster from a subsample of stars with measured radial velocities and we do not detect any significant expansion or rotation effects in the cluster. Our results suggest that the cluster is somewhat younger (about 30 Myr) than previously thought. Based on spectroscopic observations, we argue that the cluster is mass-segregated and that the distribution of spectral types shows little variation compared to other young stellar groups. Conclusions: In this study, we deliver the most complete census of cluster members that can be done with Gaia data alone and we use this new sample to provide an updated picture on the 6D structure of the cluster.
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