论文标题
了解Gaimgee和Gaia的银河系凸起的速度分布
Understanding the velocity distribution of the Galactic Bulge with APOGEE and Gaia
论文作者
论文摘要
我们以Apogee DR16和{\ it Gaia} dr2的形式重新审视银河凸起/条区域中的恒星速度分布,特别是在可能的高速度(HV)峰及其物理起源上。我们使用两个不同的模型拟合速度分布,即使用高斯 - 热线多项式和高斯混合模型(GMM)。使用Gauss-Hermite多项式的拟合结果揭示了速度分布的平均速度($ \ bar {V} $)与“偏度”($ h_ {3} $)之间的正相关性,可能是由银河系杆引起的。 $ n = 2 $ gmm拟合显示$ |μ_{2} | $和$σ_{2} $的对称纵向趋势(平均速度和次要组件的标准偏差)与$ x_ {2} $ orbital家庭预测不一致。在$ | l | \ sim6^\ circ $中可以看到冷次级峰。但是,借助来自{\ it gaia}的其他切向信息,我们发现凸起中的HV星形在径向区分速度分布中显示出相似的模式($ v _ {\ rm rm r} -v _ {\ rm t} $),无论如何存在,无论存在与明显的冷HV峰。观察到的$ v _ {\ rm r} -v _ {\ rm t} $(或$ v _ {\ rm gsr}-μ__{l} $)分布与简单的MW bar模型的预测一致。从ASPCAP和CANNON推断出的化学丰度和年龄表明,凸起/棒中的HV恒星通常比凸起/棒区域中的其他恒星年龄(如果不大)。
We revisit the stellar velocity distribution in the Galactic bulge/bar region with APOGEE DR16 and {\it Gaia} DR2, focusing in particular on the possible high-velocity (HV) peaks and their physical origin. We fit the velocity distributions with two different models, namely with Gauss-Hermite polynomial and Gaussian mixture model (GMM). The result of the fit using Gauss-Hermite polynomials reveals a positive correlation between the mean velocity ($\bar{V}$) and the "skewness" ($h_{3}$) of the velocity distribution, possibly caused by the Galactic bar. The $n=2$ GMM fitting reveals a symmetric longitudinal trend of $|μ_{2}|$ and $σ_{2}$ (the mean velocity and the standard deviation of the secondary component), which is inconsistent to the $x_{2}$ orbital family predictions. Cold secondary peaks could be seen at $|l|\sim6^\circ$. However, with the additional tangential information from {\it Gaia}, we find that the HV stars in the bulge show similar patterns in the radial-tangential velocity distribution ($V_{\rm R}-V_{\rm T}$), regardless of the existence of a distinct cold HV peak. The observed $V_{\rm R}-V_{\rm T}$ (or $V_{\rm GSR}-μ_{l}$) distributions are consistent with the predictions of a simple MW bar model. The chemical abundances and ages inferred from ASPCAP and CANNON suggest that the HV stars in the bulge/bar are generally as old as, if not older than, the other stars in the bulge/bar region.