论文标题
$ Gaia $ rr Lyrae的化学仪器：光环和光盘
Chemo-kinematics of the $Gaia$ RR Lyrae: the halo and the disc
论文作者
论文摘要
我们介绍了由$ Gaia $检测到的大型RR Lyre样本的多组分运动学模型的结果。通过强加四倍的对称性并采用$ GAIA $适当的动作，我们可以从银河系中心推断出速度椭圆形的行为。我们检测到两个不同组成部分的存在：主要的非旋转晕样种群和类似旋转的圆盘状种群。我们证明了光环lyrae可以描述为各向同性和径向偏置部分的叠加。光晕的径向偏置部分的特征是高轨道各向异性$β\ obβ\ oby oby oby oby ob y of0.9 $，在50 \％至80 \％的halo rr lyae lyre lyre lyre $ 5 <r $（kpc）$ <25 $中。与以前的研究一致，我们将此高$β$组件解释为古代大规模合并的碎片云，也称为$ gaia $ sausage（GS），我们的轨道极值是我们约束的。 RR Lyrae的灯曲线特性支持运动学分解：GS恒星更富含金属，并且具有与各向同性光晕分量相比，Oosterhoff 1型1型和高振幅短期（HASP）变量更高。金属性/HASP地图表明，光环的内部10 kPC可能是由现场的RR Lyre居住的。圆盘lyre lyre的平均方位速度和速度分散至$ r \ 30 $ kpc与年轻和金属富含金属富的薄碟片恒星种群的行为一致。
We present the results of a multi-component kinematic model of a large sample of RR Lyrae detected by $Gaia$. By imposing a four-fold symmetry and employing $Gaia$ proper motions, we are able to infer the behaviour of the velocity ellipsoid between $\approx3$ and $\approx30$ kpc from the centre of the Galaxy. We detect the presence of two distinct components: a dominant non-rotating halo-like population and a much smaller rotating disc-like population. We demonstrate that the halo RR Lyrae can be described as a superposition of an isotropic and radially-biased parts. The radially-biased portion of the halo is characterised by a high orbital anisotropy $β\approx0.9$ and contributes between 50\% and 80\% of the halo RR Lyrae at $5<R$(kpc)$<25$. In line with previous studies, we interpret this high-$β$ component as the debris cloud of the ancient massive merger also known as the $Gaia$ Sausage (GS) whose orbital extrema we constrain. The lightcurve properties of the RR Lyrae support the kinematic decomposition: the GS stars are more metal-rich and boast higher fractions of Oosterhoff Type 1 and high amplitude short period (HASP) variables compared to the isotropic halo component. The metallicity/HASP maps reveal that the inner 10 kpc of the halo is likely inhabited by the RR Lyrae born in-situ. The mean azimuthal speed and the velocity dispersion of the disc RR Lyrae out to $R\approx30$ kpc are consistent with the behaviour of a young and metal-rich thin disc stellar population.
