Gaia Data Release 2 Mapping the Milky Way disc kinematics
Gaia Data Release 2 Mapping the Milky Way disc kinematics
复制标题
盖亚数据第 2 版绘制银河系圆盘运动学图
DOI：
10.1051/0004-6361/201832865
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发表时间：
2018
影响因子：
6.5
通讯作者：
La
中科院分区：
文献类型：
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作者：
Katz D;Antoja T;Romero Gomez M;Drimmel R;Reyle C;Seabroke G M;Soubiran C;Babusiaux C;Di Matteo P;Figueras F;Poggio E;Robin A C;Evans D W;Brown A G A;Vallenari A;Prusti T;de Bruijne J H J;Bailer Jones C A L;Biermann M;Eyer L;Jansen F;Jordi C;Klioner S A;La
第二个盖亚数据版本 (GaiaDR2) 包含 13 亿个光源的高精度位置、视差和自行，以及 720 万颗亮度高于 GRVS= 12 星等的恒星的视距速度。两个样本都提供了完整的天空覆盖范围。目的为了说明 GaiaDR2 的潜力，我们首先观察了围绕太阳几千秒差距半径内的银河系圆盘的运动学。方法我们首次受益于 640 万颗 F-G-K 恒星的样本，这些恒星具有完整的 6D 相空间坐标、精确的视差 (σϖ∕ϖ≤ 20%) 和精确的银河圆柱速度（所有三个分量的不确定性中位数为 0.9-1.4 km s-1，20% 的恒星不确定性小于 1 km s-1）。从这个样本中，我们提取了 320 万颗巨星的子样本，以绘制银河盘的速度场，距银河中心约 5 kpc 至约 13 kpc，平面上方和下方最多 2 kpc。我们还研究了 30 万颗太阳邻域恒星 (r< 200 pc) 在速度空间中的分布，中值速度不确定性为 0.4 km s-1，并使用完整样本来研究超密度如何在更遥远的区域中演化。结果GaiaDR2 使我们能够以前所未有的准确度、精度和空间分辨率绘制银河中心中值速度和速度色散的 3D 地图。这些地图显示了银盘速度场的复杂性和丰富性。我们观察速度所有分量的流运动以及速度色散的模式。例如，我们确认了先前报道的内盘和外盘分别具有负和正的半乳心径向速度梯度。在这里，我们将它们视为非轴对称运动振荡的一部分，并绘制了其方位角和垂直行为。我们还见证了太阳邻域速度平面和遥远区域中恒星的新的全球排列，其中恒星被组织成薄的亚结构，其形状为圆拱形，大致沿着 U−V 平面中的水平方向定向。此外，在遥远的区域，我们比以往任何时候都更清楚地看到速度子结构的变化，特别是大力神流的速度变化。 结论GaiaDR2 提供了现有最大的全 6D 相空间坐标目录。相对于 GaiaDR1，它还大大增加了可用距离和横向速度的数量。例如，GaiaDR2 提供了有关银河系的大量信息，并揭示了银盘内清晰的非轴对称运动特征。现在，天文学界需要探索其全部潜力。
ContextThe secondGaiadata release (GaiaDR2) contains high-precision positions, parallaxes, and proper motions for 1.3 billion sources as well as line-of-sight velocities for 7.2 million stars brighter thanGRVS= 12 mag. Both samples provide a full sky coverage.AimsTo illustrate the potential ofGaiaDR2, we provide a first look at the kinematics of the Milky Way disc, within a radius of several kiloparsecs around the Sun.MethodsWe benefit for the first time from a sample of 6.4 million F-G-K stars with full 6D phase-space coordinates, precise parallaxes (σϖ∕ϖ≤ 20%), and precise Galactic cylindrical velocities (median uncertainties of 0.9-1.4 km s-1and 20% of the stars with uncertainties smaller than 1 km s-1on all three components). From this sample, we extracted a sub-sample of 3.2 million giant stars to map the velocity field of the Galactic disc from ~5 kpc to ~13 kpc from the Galactic centre and up to 2 kpc above and below the plane. We also study the distribution of 0.3 million solar neighbourhood stars (r< 200 pc), with median velocity uncertainties of 0.4 km s-1, in velocity space and use the full sample to examine how the over-densities evolve in more distant regions.ResultsGaiaDR2 allows us to draw 3D maps of the Galactocentric median velocities and velocity dispersions with unprecedented accuracy, precision, and spatial resolution. The maps show the complexity and richness of the velocity field of the galactic disc. We observe streaming motions in all the components of the velocities as well as patterns in the velocity dispersions. For example, we confirm the previously reported negative and positive galactocentric radial velocity gradients in the inner and outer disc, respectively. Here, we see them as part of a non-axisymmetric kinematic oscillation, and we map its azimuthal and vertical behaviour. We also witness a new global arrangement of stars in the velocity plane of the solar neighbourhood and in distant regions in which stars are organised in thin substructures with the shape of circular arches that are oriented approximately along the horizontal direction in theU−Vplane. Moreover, in distant regions, we see variations in the velocity substructures more clearly than ever before, in particular, variations in the velocity of the Hercules stream.ConclusionsGaiaDR2 provides the largest existing full 6D phase-space coordinates catalogue. It also vastly increases the number of available distances and transverse velocities with respect toGaiaDR1.GaiaDR2 offers a great wealth of information on the Milky Way and reveals clear non-axisymmetric kinematic signatures within the Galactic disc, for instance. It is now up to the astronomical community to explore its full potential.