Asymmetric metallicity patterns in the stellar velocity space with RAVE-猫眼课题宝

DOI：

10.1051/0004-6361/201629387

发表时间：

2017-02

期刊：

Astronomy and Astrophysics

影响因子：

6.5

通讯作者：

中科院分区：

物理与天体物理2区

文献类型：

作者：

T. Antoja;G. Kordopatis;A. Helmi;G. Monari;B. Famaey;R. Wyse;E. Grebel;M. Steinmetz;J. Bland-Hawthorn;B. Gibson;O. Bienaymé;J. Navarro;Q. Parker;W. Reid;G. Seabroke;A. Siebert;A. Siviero;T. Zwitter

上下文恒星的化学丰度编码了关于它们起源的地点和时间的信息。例如，在星团中一起形成的恒星应该呈现化学均匀性。此外，受到棒臂和旋臂影响的盘星可能会有不同的化学特征，这取决于它们所遵循的轨道类型，例如来自银河系内部与外部区域。目标。我们探讨速度和金属丰度之间的相关性和可能的独特的化学签名的速度超密度的本地银河系邻域。我们使用大型光谱巡天RAVE和日内瓦哥本哈根巡天。我们比较了速度平面（v R，v φ）中区域的金属丰度分布与对称区域（−v R，v φ）的金属丰度分布。我们预计类似的金属丰度分布，如果没有示踪剂的子人口（例如，一个分散的集群，吸积星），如果磁盘的银河系是轴对称的，如果酒吧和螺旋臂的轨道效应是弱的。我们发现，太阳附近的金属度速度空间是高度图案化的。大部分的速度平面显示的金属丰度分布的差异时，比较对称的V R区域。中位金属丰度的典型差异为0.05 dex，具有统计学显著性（至少95%置信度），且值高达0.6 dex。对于低方位角速度v φ的恒星，向外运动的恒星。这些包括武仙座和毕宿星运动群中的恒星以及其他类似速度分支的结构。对于较高的v φ，向内运动的恒星比向外运动的恒星具有更高的金属丰度。除了已知的厚盘和薄盘的正梯度和负梯度外，我们还发现在高金属丰度时v φ与金属丰度的正梯度。对金属丰度不对称性最可能的解释是，它主要是由于银河棒的轨道效应和盘的径向金属丰度梯度。我们提出了一个模拟，支持这一想法。

Context. The chemical abundances of stars encode information on their place and time of origin. Stars formed together in e.g. a cluster, should present chemical homogeneity. Also disk stars influenced by the effects of the bar and the spiral arms might have distinct chemical signatures depending on the type of orbit that they follow, e.g. from the inner versus outer regions of the Milky Way. Aims. We explore the correlations between velocity and metallicity and the possible distinct chemical signatures of the velocity over-densities of the local Galactic neighbourhood.Methods. We use the large spectroscopic survey RAVE and the Geneva Copenhagen Survey. We compare the metallicity distribution of regions in the velocity plane (v R ,v φ ) with that of their symmetric counterparts (−v R ,v φ ). We expect similar metallicity distributions if there are no tracers of a sub-population (e.g. a dispersed cluster, accreted stars), if the disk of the Galaxy is axisymmetric, and if the orbital effects of the bar and the spiral arms are weak.Results. We find that the metallicity-velocity space of the solar neighbourhood is highly patterned. A large fraction of the velocity plane shows differences in the metallicity distribution when comparing symmetric v R regions. The typical differences in the median metallicity are of 0.05 dex with statistical significant of at least 95% confidence, and with values up to 0.6 dex. For stars with low azimuthal velocity v φ , the ones moving outwards. These include stars in the Hercules and Hyades moving groups and other velocity branch-like structures. For higher v φ , the stars moving inwards have higher metallicity than those moving outwards. We have also discovered a positive gradient in v φ with respect to metallicity at high metallicities, apart from the two known positive and negative gradients for the thick and thin disks.Conclusions. The most likely interpretation of the metallicity asymmetry is that it is mainly due to the orbital effects of the Galactic bar and the radial metallicity gradient of the disk. We present a simulation that supports this idea.

Asymmetric metallicity patterns in the stellar velocity space with RAVE

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