Collaborative Research: Exploring the Dark Side of NGC 5128

研究人员将研究距离最近的半人马座A巨型椭圆星系的外围，以了解该星系如何在宇宙时间内积累其恒星和暗物质质量。研究人员已经测量了几乎所有与半人马座A有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。利用对星团集合及其围绕半人马座A的运动的观测，研究人员将测量该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大型星团，即被较大的半人马座A吞噬后较小星系遗留下来的大型星团。通过详细研究这些星团的运动，以及它摧毁的较小星系，他们将对半人马座A的“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。研究人员将在国家科学基金会的基特峰国家天文台向游客展示该项目的科学成果，方法是在游客中心实施一项新的讲解员培训计划。研究人员将前往布莱斯峡谷国家公园，通过暑期实习展示他们的结果，最终向1.6万名游客传授夜空知识。目前流行的冷暗物质模型对星系大小的光晕的亚晕质量函数和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的暗物质密度分布将通过使用从几乎完整的星团样本获得的运动学来测量，并与最近的模拟结果进行比较，这些模拟表明，最近合并和活动的星系核应该具有浅的暗物质分布。通过将星团运动学与现有的红巨星分支星图相结合，可以识别和加权可见的、被吸积的子结构。最后，将分析一个完整的超致密矮星样本，包括将它们识别为剥离矮星系的中心致密残留物的搜索。考虑到这种亚晕的数量是该计划的一个新方面，也是在测试星系形成模型时基本上被忽视的一个方面。这些努力将在我们最近的椭圆星系邻居检验亚星系尺度的冷暗物质模型的主要预测。这一奖项反映了NSF的法定任务，并通过使用基金会的智力优势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.