论文标题
识别Gaia Dr2中银河棒的共振：ii。角度的线索
Identifying resonances of the Galactic bar in Gaia DR2: II. Clues from angle space
论文作者
论文摘要
银河系磁盘表现出仍具有动力学来源的复杂轨道子结构。角度变量$（θ_ϕ，θ_r）$ - 与操作$（l_z，j_r）$相连，并描述恒星沿其轨道的位置 - 是通过轨道形状$δθ_R /δθ_θ_θ_θ_=-$δθ_θ_θ= -m / l $识别$ l $：$ m $：$ l $：$ l $：$ m $：过去，角度签名已被调查选择效果（SES）隐藏。使用禁止的星系的测试粒子模拟，我们证明\ emph {gaia}应该使我们能够在角度空间中识别银河棒的外部lindblad共振（$ l =+1，m = 2 $，OLR）。我们研究克服SES的策略。在\ emph {gaia} dr2 rvs样本的角度数据中，我们独立地标识了OLR的四个候选物，因此对于模式速度$ω__\ text {bar} $。最强大的候选人，$ω_\ text {bar} \sim1.4Ω_0$，将OLR定位在“ Sirius”移动组上方，同意银河中心的测量值，并且可以在“ Hercules/horn”周围的高阶共振支撑。但是，正如伴侣的动作研究中所讨论的那样，它错过了经典的轨道取向翻转。候选$ω__\ text {bar} \sim1.2Ω_0$也是由基于动作的研究提出的，在“帽子”处有OLR，与\ emph {slow bar}型号一致，但仍然受SES的影响。较弱的候选人为$ω_\ text {bar} =1.6Ω_0$和$1.74Ω_0$。此外，我们表明恒星角度不支持\ emph {fast bar}的OLR创建的“大力神/角”。我们得出的结论是，要解决“ Sirius”或“ HAT”与酒吧的OLR有关，则需要更复杂的动力解释，并且需要更加扩展的数据，并具有良好的SES。
The Milky Way disk exhibits intricate orbit substructure of still-debated dynamical origin. The angle variables $(θ_ϕ,θ_R)$ -- which are conjugates to the actions $(L_z,J_R)$, and describe a star's location along its orbit -- are a powerful diagnostic to identify $l$:$m$ resonances via the orbit shape relation $Δθ_R / Δθ_ϕ= -m/l$. In the past, angle signatures have been hidden by survey selection effects (SEs). Using test particle simulations of a barred galaxy, we demonstrate that \emph{Gaia} should allow us to identify the Galactic bar's Outer Lindblad Resonance ($l=+1, m=2$, OLR) in angle space. We investigate strategies to overcome SEs. In the angle data of the \emph{Gaia} DR2 RVS sample, we independently identify four candidates for the OLR and therefore for the pattern speed $Ω_\text{bar}$. The strongest candidate, $Ω_\text{bar}\sim1.4Ω_0$, positions the OLR above the `Sirius' moving group, agrees with measurements from the Galactic center, and might be supported by higher-order resonances around the `Hercules/Horn'. But it misses the classic orbit orientation flip, as discussed in the companion study on actions. The candidate $Ω_\text{bar}\sim1.2Ω_0$ was also suggested by the action-based study, has the OLR at the `Hat', is consistent with \emph{slow bar} models, but still affected by SEs. Weaker candidates are $Ω_\text{bar}=1.6Ω_0$ and $1.74Ω_0$. In addition, we show that the stellar angles do not support the `Hercules/Horn' being created by the OLR of a \emph{fast bar}. We conclude that -- to resolve if `Sirius' or `Hat' is related to the bar's OLR -- more complex dynamical explanations and more extended data with well-behaved SEs are required.
