发表机构
Universidad de La Laguna; Instituto de Astrofísica de Canarias; Université de Strasbourg（拉各拉纳加大学; 加那利天体物理研究所; 斯特拉斯堡大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
利用盖亚DR3中1.1亿颗恒星的垂直自行，首次直接测量银河系盘倾斜速率为14±2度/吉年，并推断其源于约80-100亿年前的一次重大并合事件，为盘星系组装历史提供新探针。
AI 中文摘要
银河系盘在最低阶近似下通常被描述为一个具有固定自转轴的扁平旋转恒星成分。然而，与较小星系的相互作用和并合预期会对盘的性质产生影响。这类相互作用会在星系盘中留下持久的痕迹，包括已在银河系中探测到的翘曲和波纹波，此外还有盘的缓慢重新定向，即所谓的倾斜，而这一现象至今从未被直接测量过。在此，我们利用盖亚DR3星表中1.1亿颗恒星的垂直自行，首次对银河系盘的倾斜速率进行了直接测量。探测到的信号为14±2度/吉年，围绕太阳-银心轴，具有统计显著性，并与宇宙学模拟中发现的典型值一致。通过将我们的测量与高分辨率定制模拟进行比较，我们推断观测到的倾斜速率很可能是约80-100亿年前发生的一次重大吸积事件的长期后果。该信号与一颗在逆行轨道上、质量比约为1:4的大质量卫星星系并合一致，可能与盖亚-恩克拉多斯/香肠事件相关。这些结果为银河系形成历史中的一个关键事件提供了独立证据，并引入了一种从盘星系当前运动重建其组装历史的新方法。
英文摘要
The Milky Way disc is typically described, at lowest order, as a flattened rotating stellar component with a fixed spin axis. However, interactions and mergers with smaller galaxies are expected to have an impact on the disc properties. Such interactions can leave long-lasting signatures within galactic discs, including warps and corrugation waves that have already been detected in the Milky Way, but also a slow reorientation of the disc known as tilting, which has never been directly measured up to now. Here, using the vertical proper motions of 110 million stars from the Gaia DR3 catalogue, we present the first-ever direct measurement of the tilting rate of our Galaxy's disc. The detected signal of 14 +/- 2 deg/Gyr around the Sun-Galactic Centre axis is statistically significant and is consistent with typical values found in cosmological simulations. By comparing our measurements with high-resolution tailored simulations, we infer that the observed tilting rate is likely the long-term consequence of a major accretion event that occurred around 8-10 billion years ago. The signal is consistent with the merger of a massive satellite galaxy on a retrograde orbit with a ratio of about 1:4, probably associated with the Gaia-Enceladus/Sausage event. These results provide independent evidence for a key episode in the Milky Way's formation history and introduce a new way to reconstruct the assembly histories of disc galaxies from their present-day motions.
CommentsSubmitted to journal on 04/09/2026
