Dissecting the Sub-Structured Halo

Steven Majewski博士（弗吉尼亚大学）和他的团队将进行一套五项主要实验，这将扩大对已知银河系晕潮流的普查，并利用晕流来了解星系演化、结构形成和星系尺度上的暗物质（DM）。这些实验(1)是研究化学的光环潮汐流使用的恒星流中阶梯光栅光谱光学和近红外波长来验证发现射手座的主要部门的金属丰度梯度流,(2)的研究中包含的恒星流的三维运动地面自行调查的54片Kapteyn出现选择区域领域获得流轨道和限制银河系的形状和强度潜力,(3)利用绿岸望远镜对潮汐流中的m型巨星样本进行初步研究，寻找明亮的水脉，以便使用甚大基线阵列对潮汐流进行精确的天体测量；(4)对光度网格巨星巡天进行光谱跟踪，该巡天已经确定了许多以前已知的和新发现的横跨天空两个半球的光晕亚结构；(5)更全面地描述了G和K巨星的空间和径向速度分布，这些恒星看起来像是该研究小组在大小麦哲伦云周围发现的“经典”恒星晕。银河系晕的恒星成分为星系形成理论提供了一个重要的试验台。目前的“一致性”，分层DM宇宙学预测恒星流作为吸积亚晕的潮汐残余物的存在。因此，发现和描述这些流提供了重要的信息，以约束Cold dm预测的合并历史的性质。这些流也是高度敏感的动态探测器，限制了银河系晕的形状、强度和块状，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的学生领导和贡献推动的。每个实验都是由不同的研究生领导的，或者将由不同的研究生领导，作为他们博士论文的一部分。

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.