探测从太阳邻近区到外星系的晕：将局部速度结构中的恒星与大尺度云联系起来
Probing the Halo From the Solar Vicinity to the Outer Galaxy: Connecting Stars in Local Velocity Structures to Large-Scale Clouds
摘要：
本文介绍了在M巨星巡天中发现的速度空间中的两个局部特征与恒星在全球尺度上的空间不均匀性之间的第一个联系。比较宇宙学，化学动力学恒星晕模型证实，M巨星人口是特别敏感的罕见，最近和大规模的吸积事件。这些事件可产生当地观测到的速度序列-这是一个共同起源的一小部分碎片在其偏心轨道的近心附近高速穿过勘测体积的特征。大多数碎片是在大得多的结构中发现的，其形态更像云而不是流，位于轨道远心。采用这种解释，全空间的运动所代表的观测速度特征推导出的假设下，每个序列内的成员共享一个共同的速度。然后，轨道积分被用来追踪这些恒星在天空中过去和未来的轨迹，揭示与以前发现的大型云状结构的合理关联。在附近的速度结构和这些遥远的云之间建立的联系是为绘制这种巨大碎片系统的连贯地图而采取的初步步骤。这些地图有望为碎片云的起源提供新的见解，对银河系历史和结构的新探测，以及对本地暗物质分布的高速尾部的新约束，这些对解释直接探测实验至关重要。
英文摘要：
(Abridged) This paper presents the first connections made between two local features in velocity-space found in a survey of M giant stars and stellar spatial inhomogeneities on global scales. Comparison to cosmological, chemodynamical stellar halo models confirm that the M giant population is particularly sensitive to rare, recent and massive accretion events. These events can give rise to local observed velocity sequences - a signature of a small fraction of debris from a common progenitor, passing at high velocity through the survey volume, near the pericenters of their eccentric orbits. The majority of the debris is found in much larger structures, whose morphologies are more cloud-like than stream-like and which lie at the orbital apocenters. Adopting this interpretation, the full-space motions represented by the observed velocity features are derived under the assumption that the members within each sequence share a common velocity. Orbit integrations are then used to trace the past and future trajectories of these stars across the sky revealing plausible associations with large, previously-discovered, cloud-like structures. The connections made between nearby velocity structures and these distant clouds represent preliminary steps towards developing coherent maps of such giant debris systems. These maps promise to provide new insights into the origin of debris clouds, new probes of Galactic history and structure, and new constraints on the high-velocity tails of the local dark matter distribution that are essential for interpreting direct detection experiments.
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