Primordial Dark Matter Halos and the Present Mass Distributions of Galaxies

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。McGaugh博士将继续他的工作，以确定盘星系的不同组成部分的质量，特别是恒星盘，气体盘和暗晕。 他将在电离气体的H-α线和中性氢中收集速度分辨地图，以测量星系盘中气体的密度及其速度场，大约100个盘星系具有广泛的属性。 他将使用近红外K波段图像来确定恒星质量的分布，拟合旋转曲线以获得不同成分的质量贡献。 在暗晕主导引力的低表面亮度磁盘中，他将使用测量的速度场来搜索通过标准冷暗物质模拟预测的陡峭内部尖点的证据。 较大的星系样本将被用来通过适当的绝热压缩处理来获得初始晕质量分布。 最后，他将校准一个经验的质量差异-加速度关系。 质量差异被局部定义为观测到的旋转圆周速度与仅从气体和恒星预测的旋转圆周速度之间的差异。这种差异与圆盘物质的轨道速度有关;本研究旨在更好地描述这种关系，作为理解其起源的一步。McGaugh博士将继续他的小学生推广计划。 他将把这项研究的数据产品和模型发布到一个网页上的天文学界。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Dr. McGaugh will continue his work to determine the masses of the different components of disk galaxies, in particular the stellar disk, the gaseous disk and the dark halo. He will assemble velocity-resolved maps in the H-alpha line of ionized gas and in neutral hydrogen, to measure the density of gas in the galaxy disk, and its velocity field, for about 100 disk galaxies with a wide range in properties. He will use near-infrared K-band images to determine the distribution of stellar mass, fitting the rotation curves to obtain the mass contributions of the different components. In the low-surface-brightness disks where the dark halo dominates the gravitational forces, he will use the measured velocity field to search for evidence of the steep inner cusp predicted by simulations with standard Cold Dark Matter. The larger sample of galaxies will be used to derive the initial halo mass profiles by proper treatment of adiabatic compression. Finally, he will calibrate an empirical mass-discrepancy--acceleration relation. The mass discrepancy is defined locally as the difference between the observed circular speed of rotation and that predicted from the gas and stars alone. This discrepancy is related to the orbital speed of disk material; the present study aims to characterize that relation better as a step towards understanding its origin.Dr McGaugh will continue his program of outreach to elementary-school children. He will distribute the data products and models from this study to the astronomical community on a web page.