[论文解读] Proper motions of young stars in Chamaeleon. II. New kinematical candidate members of Chamaeleon I and II

Belén López Martí, F. Jiménez-Esteban+5 more|arXiv (Cornell University)|Jul 12, 2013

Stellar, planetary, and galactic studies参考文献 31被引用 13

一句话总结

本研究利用UCAC4星等的自行数据和光谱能量分布拟合，分别识别出51个和14个船尾座I和II移动星群的新型运动学候选成员。这些候选成员主要为无盘、低质量恒星（0.3–1.4 M☉），年龄≤20 Myr，位于主暗云核之外，表明这些移动星群的分布范围可能比以往认为的更广。

ABSTRACT

The Chamaeleon star-forming region has been extensively studied in the last decades. However, most studies have been confined to the densest parts of the clouds. In a previous paper, we analysed the kinematical properties of the spectroscopically confirmed population of the Chamaeleon I and II clouds. We now report on a search for new kinematical candidate members to the Chamaeleon I and II moving groups using available information from public databases and catalogues. Our candidates were initially selected in an area of 3 deg around each cloud on the basis of proper motions and colours from the UCAC4 Catalog. The SEDs of the objects were constructed using photometry retrieved from the Virtual Observatory and other resources, and fitted to models of stellar photospheres to derive effective temperatures, gravity values, and luminosities. Masses and ages were estimated by comparison with theoretical evolutionary tracks in a Hertzprung-Russell diagram. We have identified 51 and 14 candidate members to the Chamaeleon I and II moving groups, respectively, of which 17 and 1, respectively, are classified as probable young stars (ages < 20 Myr) according to our analysis. Another object in Chamaeleon I located slightly above the 1 Myr isochrone is classified as a possible young star. All these objects are diskless stars with masses in the range 0.3M-1.4MSun, and ages consistent with those reported for the corresponding confirmed members. They tend to be located at the boundaries of or outside the dark clouds, preferably to the north-east and south-east in the case of Chamaeleon I, and to the north-east in the case of Chamaeleon II. We conclude that the kinematical population of Chamaeleon I and II could be larger and spread over a larger area of the sky than suggested by previous studies.

研究动机与目标

• 识别船尾座I和II移动星群在暗云最致密区域之外的新型候选成员。
• 利用多波段测光和SED建模，表征这些候选成员的运动学、测光和演化特性。
• 检验船尾座I和II的年轻恒星群体是否局限于当前的暗云结构，还是在空间上有所延伸。
• 通过自行和颜色选择结合SED分析，评估移动星群群体的完整性和空间范围。

提出的方法

• 基于UCAC4星表中的自行和颜色数据，结合已知移动星群的运动学特征，初步筛选运动学候选成员。
• 利用虚拟天文台及其他公开数据库的测光数据构建谱能分布（SED）。
• 将SED与恒星大气模型拟合，推导有效温度、表面重力、光度和恒星质量。
• 通过将推导出的参数与赫罗图中的理论前主序演化轨迹比较，估算年龄。
• 将年龄≤20 Myr的天体选为船尾座I和II移动星群的可能成员。
• 进行空间和运动学分析，评估其相对于主要暗云区域的分布特征。

实验结果

研究问题

• RQ1 在暗云最致密区域之外，是否存在船尾座I和II移动星群的额外年轻恒星成员？
• RQ2 这些新识别出的运动学候选成员相对于主要云结构的空间分布如何？
• RQ3 候选成员的物理参数（质量、年龄、光度）是否支持其属于船尾座I和II移动星群？
• RQ4 基于以核心为中心的研究，船尾座I和II移动星群的群体是否比以往认为的更广泛延伸？

主要发现

• 基于自行和颜色选择，共识别出51个船尾座I和14个船尾座II的新型运动学候选成员。
• 其中，船尾座I的17个候选成员和船尾座II的1个候选成员通过SED分析被归类为可能的年轻恒星，其年龄与移动星群群体一致。
• 船尾座I中另有一个天体，位于1 Myr等龄线稍上方，被归类为可能的年轻恒星。
• 所有确认的年轻候选成员均为无盘恒星，质量范围为0.3 ≤ M/M☉ ≤ 1.4，年龄≤20 Myr。
• 这些候选成员主要位于主暗云的边界或外部区域，尤其在船尾座I的东北和东南方向，以及船尾座II的东北方向。
• 结果表明，船尾座I和II移动星群的群体可能比以往认识的覆盖更广的天空区域。