Collaborative Research: Exploring the Dark Side of NGC 5128

研究人员将研究最近的巨型椭圆星系半人马座A的外围，以了解该星系是如何在宇宙时间内形成恒星和暗物质质量的。研究人员已经测量了几乎所有与半人马座A相关的发光星团的位置，并将使用大型地面望远镜精确测量它们的速度。通过对这些星团的观测，以及它们在半人马座A周围的运动，研究人员将测量星系的暗物质密度分布，并寻找与半人马座A合并的较小星系的残骸。他们观测的重要目标是识别被较大的半人马座A吞噬后遗留下来的大型星团。连同被它摧毁的较小星系，他们将对半人马座a的“黑暗面”有一个完整的清单。他们的结果将应用于对所有星系群的研究。研究人员将通过在游客中心实施一项新的讲解员培训计划，向国家科学基金会基特峰国家天文台的游客展示这项计划的科学成果。调查人员将前往布莱斯峡谷国家公园（Bryce Canyon National Park），通过夏季实习的方式展示他们的研究结果，最终向1.6万名游客介绍夜空。目前最受欢迎的冷暗物质模型对亚晕质量函数和星系大小晕的暗物质密度分布做出了明确的预测，但定量验证这些预测是具有挑战性的。半人马座A的暗物质密度分布图将被测量，使用从几乎完整的星团样本中获得的运动学，并将结果与最近的模拟结果进行比较，这些模拟结果表明，最近合并的星系和活跃的星系核应该具有较浅的暗物质分布图。通过将星团的运动学与已经存在的红巨星分支星图相结合，可见的、被吸积的子结构将被识别和权衡。最后，将分析一个完整的超致密矮星样本，包括将它们确定为剥离矮星系的中心致密残留物的搜索。计算亚晕的数量是这个项目的一个新方面，也是在测试星系形成模型时很大程度上被忽视的一个方面。这些努力将在离我们最近的椭圆星系邻居的亚星系尺度上测试冷暗物质模型的主要预测。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The investigators will study the outskirts of the nearest giant elliptical galaxy, named Centaurus A, to learn how the galaxy built up its stellar and dark matter mass over cosmic time. The investigators have measured the positions of nearly all the luminous star clusters associated with Centaurus A, and will precisely measure their velocities using large ground-based telescopes. Using observations of the collection of star clusters, and their motions around Centaurus A, the investigators will measure the dark matter density profile of the galaxy, and search for remnants of smaller galaxies that have merged with Centaurus A. The important goal of their observations is identifying large star clusters which are the remnants left over from smaller galaxies after they have been devoured by the larger Centaurus A. By studying the motions of these star clusters in detail, along with the smaller galaxies it has destroyed, they will have a complete inventory of the 'dark side' of Centaurus A. Their results will be applied to studies of all galaxy populations. The investigators will present the science results from this program to visitors at the National Science Foundation's Kitt Peak National Observatory, by implementing a new docent training program at the visitor center. The investigators will travel to Bryce Canyon National Park and present their results, through summer internships, which ultimately teach 16,000 visitors about the night sky.The currently favored cold dark matter model makes clear predictions for the sub-halo mass function and dark matter density profile of galaxy-sized halos, but quantitatively verifying these predictions is challenging. Centaurus A's dark matter density profile will be measured, using the kinematics derived from a nearly complete sample of star clusters, and the results compared to recent simulations that suggest galaxies with recent mergers and active galactic nuclei should have shallow dark matter profiles. By combining the star cluster kinematics with an already existing red giant branch star map, the visible, accreted substructures will be identified and weighed. Finally, a complete sample of ultra-compact dwarfs will be analyzed, including a search identifying them as the central compact remnants of stripped dwarf galaxies. Accounting for this population of sub-halos is a novel aspect of this program, and one that has largely been neglected when testing galaxy formation models. These efforts will test major predictions of the cold dark matter model at sub-galactic scales in our nearest elliptical galaxy neighbor.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.