Collaborative Research: Dwarf Galaxies and the Nature of Dark Matter

暗物质(DM)的性质仍然是当今宇宙学中尚未解决的主要问题之一，而且由于缺乏对粒子本身的任何直接检测，附近矮小星系的结构仍然是了解暗物质的温度和自我相互作用性质的最有希望的途径之一，因为任何偏离标准冷暗物质模型的情况都应该发生在低质量时。关于宇宙中星系如何形成的现代观点涉及到某种形式的“分级”过程，通过这个过程，小系统逐渐合并成更大的系统，如我们的银河系。这一范式的一个关键要素是关于合并如何进行的，这反过来又依赖于理解在观测到的宇宙寿命内推动星系形成所需的DM的性质。矮星系是具有Dm的最小、最简单的实体，它也包含以恒星和/或气体形式存在的可见重子物质。因此，它们--尤其是它们的黑色光环-代表了我们最好的局部类比，即启动了等级进程的构建块。这个项目的主要目标是使用经验技术-主要是对附近矮小星系中恒星的运动学观测--以一种在很大程度上与模型无关的方式确定这些系统中DM晕的关键属性。这个项目的具体目标包括(1)通过测量DM晕的中心质量密度和核心属性来了解DM如何在单个星系中分布，(2)探索重子物质的演化可能如何改变星系中的DM分量，(3)确定DM晕是否真的是无标度的，(4)绘制矮星DM晕的范围图，并了解它们的暗和可见成分是如何合并到我们银河系更大的晕中的，以及(5)为重建有助于我们银河系组装的原始矮星种群的性质奠定基础。这个项目建立在美国国家科学基金会几十年的仪器建造和研究拨款的基础上，以帮助我们了解DM的本质。研究人员将与几名K-12教师一起从事教育活动，进行公开演讲，并参加诸如“问天文学家”之类的活动。该项目还将在整个赠款期间支持研究生培训。

The nature of dark matter (DM) remains one of the leading unsolved problems in cosmology today, and absent any direct detection of the particles themselves, the structure of nearby dwarf galaxies remains one of the most promising avenues for learning about the temperature and self-interaction properties of DM because any deviations from the standard cold dark matter model should happen at low masses.Modern ideas regarding how galaxies form in the Universe involve some form of "hierarchical" process by which small systems progressively merged into ever larger systems like our Milky Way Galaxy. A key element of this paradigm regards how mergers proceed, which, in turn, relies on understanding the nature of the DM needed to drive the formation of galaxies within the observed lifetime of the Universe. Dwarf galaxies are the smallest, simplest entities with DM that also contain visible baryonic material in the form of stars and/or gas. As such, they---and particularly their dark halos---represent our best local analogs of the building blocks that initiated the hierarchical process. The broad goal of this project is to use empirical techniques---primarily kinematic observations of stars in nearby dwarf galaxies---to determine key properties of DM halos in these systems in a largely model-independent way.The specific aims of this project include (1) learning how DM is distributed within individual galaxies by measuring the central mass densities and core properties of DM halos, (2) exploring how the evolution of the baryonic matter may have altered the DM components in galaxies, (3) determining if DM halos are truly scale free, (4) mapping the extents of DM halos in dwarfs and understanding how their dark and visible components have merged into the greater halo of our Galaxy, and (5) laying the groundwork to reconstruct the properties of the primordial population of dwarfs that contributed to the assembly of our Galaxy. This project builds on decades of NSF-sponsored instrument building and research grants to aid our understanding of the nature of DM.The investigators will engage in educational activities with several K-12 teachers, give public talks, and participate in events such as "Ask an Astronomer." The project will also support graduate student training throughout the grant period.