$β$ Picture运动群的动力学追溯年龄
Dynamical traceback age of the $β$ Pictoris moving group
摘要：
内容：$β$风景如画的移动集团是太阳附近最着名的年轻协会之一，其中几个成员已知拥有拱星盘，行星和彗星。精确测定它的年龄是研究行星形成和盘演化等与年龄密切相关的天体物理过程的基础。目的：确定$β$ Picture移动群精确的动力学追溯年龄。方法：我们的样本结合了非常精确的盖亚DR2天体测量与地面径向速度测量均匀的方式。我们使用我们的算法的更新版本来确定动态年龄。新的方法考虑到一个强大的估计的空间和运动学协方差矩阵的协会，以改善样本选择过程中，并进行回溯分析。结果：我们估计了$β$ Pictoral运动群的$18.5_{-2.4}^{+2.0}$ Myr的动力学年龄。我们调查了出生时协会的空间结构，我们提出了一个核心的恒星更集中的存在。我们还提供了$β$ Pic的81个成员的径向速度的精确测量，其中包括10颗恒星的径向速度的首次测定。结论：我们的动态追溯年龄是三倍以上的精确比以前的追溯年龄估计，更重要的是，第一次，调和追溯年龄与其他动态，锂耗尽边界，等时年龄的最新估计。这要归功于出色的天体测量和光谱精度，我们样品的均匀性，以及对双星和成员的详细分析。
英文摘要：
Context: The $β$ Pictoris moving group is one of the most well-known young associations in the solar neighbourhood and several members are known to host circumstellar discs, planets, and comets. Measuring its age with precision is basic to study several astrophysical processes such as planet formation and disc evolution which are strongly age dependent. Aims: We aim to determine a precise and accurate dynamical traceback age for the $β$ Pictoris moving group. Methods: Our sample combines the extremely precise Gaia DR2 astrometry with ground-based radial velocities measured in an homogeneous manner. We use an updated version of our algorithm to determine dynamical ages. The new approach takes into account a robust estimate of the spatial and kinematic covariance matrices of the association to improve the sample selection process and to perform the traceback analysis. Results: We estimate a dynamical age of $18.5_{-2.4}^{+2.0}$ Myr for the $β$ Pictoris moving group. We investigated the spatial substructure of the association at birth time and we propose the existence of a core of stars more concentrated. We also provide precise radial velocity measurements for 81 members of $β$ Pic, including ten stars with the first determination of their radial velocities. Conclusions: Our dynamical traceback age is three times more precise than previous traceback age estimates and, more important, for the first time, reconciles the traceback age with the most recent estimates of other dynamical, lithium depletion boundary, and isochronal ages. This has been possible thanks to the excellent astrometric and spectroscopic precisions, the homogeneity of our sample, and the detailed analysis of binaries and membership.
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