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arXiv 2005.05054astro-ph.GA
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HR 1614移动群不是溶解群集

The HR 1614 moving group is not a dissolving cluster

Iryna Kushniruk, Thomas Bensby, Sofia Feltzing, Christian L. Sahlholdt, Diane Feuillet, Luca Casagrande

备注：
Accepted for publication in A&A
发表信息：
A&A 638, A154 (2020)
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摘要：

HR 1614在速度空间中是超密度的，长期以来一直被认为是一个古老的（~2 Gyr）和富含金属（[Fe/H]~0.2）的附近移动群，具有溶解星系团的起源。在太阳附近存在这样古老而富含金属的星系群是相当令人意外的，因为已知附近绝大多数移动的星系群都是年轻的。根据新的和更大的数据集，我们的目标是重新调查HR 1614移动群的属性和起源。为了识别和确认HR 1614移动群，我们使用了来自盖亚DR 2的天体测量数据;来自StarHorse代码的距离，消光和变红校正;来自GALAH和APOGEE光谱调查的元素丰度;以及来自SkyMapper调查的光度金属丰度。贝叶斯年龄估计SkyMapper恒星。由于武仙座流是在速度空间中最接近HR 1614移动群的运动学结构，我们使用它来进行比较。可能是这两个星系群成员的恒星是根据它们的空间速度选择的。HR 1614移动星群主要位于负U速度，在U-V空间中没有形成一个恒定能量的拱，并且在V中倾斜。它们基本上类似于在银河系薄盘和厚盘中观察到的情况，一个年轻的人口（~3 Gyr），富含金属（-0.2<[Fe/H]<0.4）和α贫乏。因此，它不应被视为一个正在溶解的疏散星团，或一个增生的星群。我们认为，HR 1614有一个复杂的起源，可以通过结合几种不同的机制，如与银河棒和螺旋结构的共振，溶解螺旋结构的相位混合，以及由于外部扰动的相位混合来解释。

英文摘要：

The HR 1614 overdensity in velocity space and has for a long time been known as an old (~2 Gyr) and metal-rich ([Fe/H]~0.2) nearby moving group that has a dissolving cluster origin. The existence of such old and metal-rich groups in the solar vicinity is quite unexpected since the vast majority of nearby moving groups are known to be young. In the light of new and significantly larger data sets we aim to re-investigate the properties and origin of the HR 1614 moving group. To identify and characterise the HR 1614 moving group we use astrometric data from Gaia DR2; distances, extinction, and reddening corrections from the StarHorse code; elemental abundances from the GALAH and APOGEE spectroscopic surveys; and photometric metallicities from the SkyMapper survey. Bayesian ages were estimated for the SkyMapper stars. Since the Hercules stream is the closest kinematical structure to the HR 1614 moving group in velocity space, we use it for comparison purposes. Stars that are likely to be members of the two groups were selected based on their space velocities. The HR 1614 moving group is located mainly at negative U velocities, does not form an arch of constant energy in the U-V space and is tilted in V. The overdensity is not chemically homogeneous but that its stars exist at a wide range of both metallicities, ages, and elemental abundance ratios. They are essentially similar to what is observed in the Galactic thin and thick disks, a younger population (~3 Gyr) that is metal-rich (-0.2<[Fe/H]<0.4) and alpha-poor. It should therefore not be considered as a dissolving open cluster, or an accreted population. We suggest that HR 1614 has a complex origin that could be explained by combining several different mechanisms such as resonances with the Galactic bar and spiral structure, phase-mixing of dissolving spiral structure, and phase-mixing due to an external perturbation.

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