论文标题
通过其红色巨型种群破译小麦芽云的运动学结构
Deciphering the Kinematic Structure of the Small Magellanic Cloud through its Red Giant Population
论文作者
论文摘要
我们使用\ Gaia \ Data Release 2目录中的数据提出了一个新的小麦芽云（SMC）的运动学模型。我们确定了属于SMC的星空统计良好的红色巨人（RG）恒星，并与公开可用的径向速度（RV）目录进行了交叉匹配。我们使用RR Lyrae为RGS创建一个3D空间模型，用于距离分布，并应用具有不同旋转属性的运动学模型和新型的潮汐膨胀处方，以生成模拟运动（PM）目录。当我们将这一系列模拟目录与观察到的RG数据进行比较时，我们发现了中等旋转的组合（距SMC中心1 kpc的$ \ sim10-20-20 $ km s $ s $^{ - 1} $，倾斜度，$ \ \ \ \ \ \ \ \ \ sim50-80 $ sim $ sim $ sim $ sim $ tem $ tem $ tem $ tem $ t n od $ te n of tens $ te n of tet n od tens $ t。扩展（缩放为$ \ sim10 $ km s $^{ - 1} $ kpc $^{ - 1} $需要解释PM签名。确切的最佳拟合参数在一定程度上取决于我们是仅评估PM还是将RV作为定性检查，从而在PM和RV结论之间留下了一些小的张力。无论哪种情况，我们的模型首选的参数空间都不同于先前推断的旋转几何形状，包括从SMC H {\ Small I}气体和仅RG RV的分析以及新的SMC PM分析，这些分析得出结论，该分析得出的结论是旋转签名无法检测到。总而言之，这强调了将SMC视为具有不同运动学的一系列不同人群的必要性。
We present a new kinematic model for the Small Magellanic Cloud (SMC), using data from the \gaia\ Data Release 2 catalog. We identify a sample of astrometrically well-behaved red giant (RG) stars belonging to the SMC and cross-match with publicly available radial velocity (RV) catalogs. We create a 3D spatial model for the RGs, using RR Lyrae for distance distributions, and apply kinematic models with varying rotation properties and a novel tidal expansion prescription to generate mock proper motion (PM) catalogs. When we compare this series of mock catalogs to the observed RG data, we find a combination of moderate rotation (with a magnitude of $\sim10-20$ km s$^{-1}$ at 1 kpc from the SMC center, inclination between $\sim50-80$ degrees, and a predominantly north-to-south line of nodes position angle of $\sim180$ degrees) and tidal expansion (with a scaling of $\sim10$ km s$^{-1}$ kpc$^{-1}$) is required to explain the PM signatures. The exact best-fit parameters depend somewhat on whether we assess only the PMs or include the RVs as a qualitative check, leaving some small tension remaining between the PM and RV conclusions. In either case, the parameter space preferred by our model is different both from previously inferred rotational geometries, including from the SMC H{\small I} gas and from the RG RV-only analyses, and new SMC PM analyses which conclude that a rotation signature is not detectable. Taken together this underscores the need to treat the SMC as a series of different populations with distinct kinematics.
