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arXiv 1801.02170astro-ph.GA
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来自RAVE数据的局部恒星动力学-- VIII。银盘扰动对红团星轨道的影响

Local Stellar Kinematics from RAVE data -- VIII. Effects of the Galactic Disc Perturbations on Stellar Orbits of Red Clump Stars

O. Onal Tas, S. Bilir, O. Plevne

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16 pages, 9 figures and 2 tables, accepted for publication in Astrophysics and Space Science
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摘要：

我们的目标是探测扩展的太阳邻域的动态结构，通过计算径向金属丰度梯度的轨道特性，这是获得轴对称和非轴对称的潜在模型，红团（RC）星从径向速度实验的第四次数据发布。距离是通过假设每颗RC星在近红外波段有一个绝对星等值，即$M_{Ks}=-1.54\pm0.04$等来获得的。利用MWPotential 2014势函数和银河棒和瞬变旋臂的扰动势函数计算了恒星轨道参数。恒星年龄的计算采用贝叶斯统计方法。径向金属丰度梯度的基础上，从银河系平面的最大垂直距离（$z_{max}$）和平面偏心率（$e_p$）的RC星的潜在模型进行评估。在$0<z_{max} \leq0.5$ kpc距离间隔中，具有$e_p\leq0.1$的子样本的最大径向金属丰度梯度为$-0.065\pm0.005$ dex kpc $^{-1}$，而具有$e_p\leq0.5$的子样本的最低值为$-0.014\pm0.006$ dex kpc $^{-1}$。我们发现，在$z_{max}>1$ kpc，径向金属丰度梯度有零或正值，他们不依赖于$e_p$子样本。薄盘存在较大的径向金属丰度梯度，而厚盘没有发现径向金属丰度梯度。此外，最大的径向金属丰度梯度获得外Lindblad共振区是有效的。我们声称，这种明显的变化，在薄光盘的径向金属丰度梯度是一个结果，源自现有的共振区域的轨道扰动。

英文摘要：

We aim to probe the dynamic structure of the extended Solar neighbourhood by calculating the radial metallicity gradients from orbit properties, which are obtained for axisymmetric and non-axisymmetric potential models, of red clump (RC) stars selected from the RAdial Velocity Experiment's Fourth Data Release. Distances are obtained by assuming a single absolute magnitude value in near-infrared, i.e. $M_{Ks}=-1.54\pm0.04$ mag, for each RC star. Stellar orbit parameters are calculated by using the potential functions: (i) for the MWPotential2014 potential, (ii) for the same potential with perturbation functions of the Galactic bar and transient spiral arms. The stellar age is calculated with a method based on Bayesian statistics. The radial metallicity gradients are evaluated based on the maximum vertical distance ($z_{max}$) from the Galactic plane and the planar eccentricity ($e_p$) of RC stars for both of the potential models. The largest radial metallicity gradient in the $0<z_{max} \leq0.5$ kpc distance interval is $-0.065\pm0.005$ dex kpc$^{-1}$ for a subsample with $e_p\leq0.1$, while the lowest value is $-0.014\pm0.006$ dex kpc$^{-1}$ for the subsample with $e_p\leq0.5$. We find that at $z_{max}>1$ kpc, the radial metallicity gradients have zero or positive values and they do not depend on $e_p$ subsamples. There is a large radial metallicity gradient for thin disc, but no radial gradient found for thick disc. Moreover, the largest radial metallicity gradients are obtained where the outer Lindblad resonance region is effective. We claim that this apparent change in radial metallicity gradients in the thin disc is a result of orbital perturbation originating from the existing resonance regions.

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