Dissecting the Sub-Structured Halo

Steven Majewski博士（弗吉尼亚大学）和他的团队将进行一系列五项主要实验，这些实验将扩大已知银河系光环潮汐流的普查，并利用光环流来了解星系演化、结构形成和暗物质（DM）在星系尺度上。 这些实验是：（1）利用光学和近红外波段的流星阶梯光谱学研究晕潮汐流的化学，以验证人马座流前缘臂金属丰度梯度的发现，（2）对54颗近双星的地基自行观测资料进行了流星三维运动的研究。赤道Kapteyn选定区域领域，以获得流轨道和约束银河系潜力的形状和强度，（3）利用绿色班克望远镜对M-在潮汐流中寻找明亮的水脉泽，这些水脉泽可用于使用甚大基线阵列对潮汐流进行精确的天体测量，（4）测光网格巨星星星巡天的光谱后续行动，该巡天已经确定了横跨天空两个半球的一些以前已知和新发现的晕子结构，（5）更全面地描述了G巨星和K巨星的空间和径向速度分布，这个研究小组在大麦哲伦星云和小麦哲伦星云周围发现的恒星晕。我们银河系晕的恒星成分为星系形成理论提供了一个重要的实验平台。目前的“和谐”，层次DM宇宙学预测存在恒星流的吸积子晕的潮汐遗迹。因此，找到和表征这些流提供了关键信息，以约束冷DM预测的合并历史的性质。这些流也是高度敏感的动力学探针，限制了银河系晕的形状，强度和块状度，并为星系的化学演化提供了关键的见解。这项研究的一个关键方面是，它主要是由本科生和研究生水平的学生领导力和贡献推动的。 每个实验都由不同的研究生领导，作为他们博士学位的一部分。论文

Dr. Steven Majewski (University of Virginia) and his team will undertake a suite of five major experiments that will both expand the census of known Milky Way halo tidal streams and exploit halo streams for the understanding of galaxy evolution, structure formation and dark matter (DM) on galaxy-scales. These experiments are (1) A study of the chemistry of halo tidal streams using echelle spectroscopy of stream stars at both optical and near-infrared wavelengths to verify the discovery of a metallicity gradient in the leading arm of the Sagittarius stream, (2) A study of the 3-D motions of stream stars contained in a ground-based proper motion survey of 54 near-equatorial Kapteyn Selected Area fields to derive stream orbits and constrain the shape and strength of the Milky Way potential, (3) Undertake a pilot study with the Green Bank Telescope of a sample of M-type giant stars in tidal streams to look for bright water masers that can be used for precision astrometry of tidal streams using the Very Large Baseline Array, (4) A spectroscopic follow-up to the photometric Grid Giant Star Survey, which has already identified a number of previously known and newly discovered halo substructures across both hemispheres of the sky, and (5) More fully characterize the spatial and radial velocity distributions of G and K giant stars in what look to be "classical" stellar halos discovered around the Large and Small Magellanic Clouds by this research group. The stellar component of our Galactic halo provides an important test-bed for theories of galaxy formation. The present "concordance", hierarchical DM cosmologies predict the presence of stellar streams as tidal remnants of accreted sub-halos. Finding and characterizing these streams thus provides crucial information to constrain the nature of the Cold DM-predicted merging history. These streams are also highly sensitive dynamical probes constraining the shape, strength and lumpiness of the halo of the Milky Way, and provide key insights into the chemical evolution of galaxies. A key aspect of this research is that it has been fueled primarily by student leadership and contributions at both the undergraduate and graduate level. Each experiment is being led or will be led by a different graduate student as part of their Ph.D. dissertation.