Mass Distribution Within Spiral Galaxies

随着天体物理学家对宇宙形成和演化的知识不断扩展，将大规模的宇宙星系形成情景与单个观测星系的测量和推断细节联系起来变得越来越可行。该项目是一个综合观测和理论研究的项目，旨在确定大量螺旋星系样本中暗物质和发光物质的分布，并将这些测量结果与协和宇宙学模型中对星系形成的预测进行比较。利用南部非洲大望远镜上的宽视场光谱成像法布里-佩罗仪器，研究人员提议获得星系的高分辨率速度图，并辅以詹斯基甚大阵列（VLA）和后来的MeerKAT（卡鲁阵列望远镜）提供的更广泛但分辨率更低的21厘米图。结合光学和近红外表面光度测量，这些数据将成为测量每个星系内总质量分布的基础。恒星群综合估计和详细的流体动力学模型将确定重子和暗物质组分的分离。大量的n体模拟将测试这些模型的稳定性，进一步确定发光物质和暗物质的各自贡献。在对重子盘的引力压缩进行校正后，这些晕模型的密度、浓度和圆周速度将与宇宙学模拟得出的预测值进行比较。差异可能为改进和扩展星系形成模拟中的物理学提供了方法。一种新的分析工具将测量星系二维运动图中的非轴对称运动模式，从而确定暗晕的形状。研究人员还将利用Fabry-Perot对早期棒状盘星系的恒星吸收线的观测来确定棒状星系的旋转速度。由于与光晕的动态摩擦减缓了棒的运动，这项测量将对这些星系的光晕密度产生另一个限制。在动力学约束下，对星系质量光比的估计旨在完善鲜为人知的圆盘星系质量光比和宽波段颜色之间的关系。在教育方面，提案小组将通过公开讲座和在新泽西州的学校向更广泛的社区传播他们的成果。他们将让本科生和研究生参与他们的研究，并指导他们在科学领域的专业发展。

As astrophysicists expand their knowledge of the formation and evolution of the Universe, tying large-scale cosmological galaxy formation scenarios to the measured and inferred details of individually observed galaxies has become increasingly feasible. This project is an integrated program of observational and theoretical studies designed to determine the distribution of both dark and luminous matter within a large sample of spiral galaxies and to compare these measurements with the predictions of galaxy formation in the concordance cosmological model.Using the wide-field spectroscopic imaging Fabry-Perot instrument on the Southern African Large Telescope, the investigators propose to obtain high-resolution velocity maps of the galaxies, supplemented with more extended but lower resolution 21-cm maps from the Jansky Very Large Array (VLA) and, later, MeerKAT (Karoo Array Telescope). Combined with optical and near-infrared surface photometry, these data will be the basis for measurement of the total mass distribution within each galaxy. Stellar population synthesis estimates and detailed hydrodynamical modeling will determine the separation into baryonic and dark matter components. Extensive N-body simulations will test the stability of the models, sharpening the determination of the separate contributions of luminous and dark matter. After correction for the gravitational compression by the baryonic disk, the density, concentration, and circular speed of these halo models will be compared to the expected values derived from cosmological simulations. Discrepancies may suggest ways to improve and extend the physics in the galaxy formation simulations. A new analysis tool will measure non-axisymmetric patterns of motion in the two-dimensional kinematic maps of the galaxies, leading to a determination of the shapes of the dark halos. The investigators will also use Fabry-Perot observations of stellar absorption lines in early-type barred disk galaxies to determine the bar's rotation speed. As dynamical friction with the halo slows the bar's motion, this measurement will yield another constraint on the halo density in these galaxies. Sharpened by dynamical constraints, estimates for the mass-to-light ratios of galaxies aim to refine the poorly-known relation between mass-to-light and broad-band colors of disk galaxies.Educationally, the proposing team will disseminate their results to the broader community through public lectures and in New Jersey schools. They will involve undergraduate and graduate students in their research and mentor them in their professional development in the sciences.