RII Track-4: Making Galaxies Out of An (Ultra) Light Invisible Matter Halo

理解大尺度结构的形成是观测宇宙学和理论宇宙学中最具挑战性的任务之一。粒子--我们今天所理解的粒子--是什么时候以及如何出现的？那么这些粒子是如何继续产生天文观测中所熟悉的大规模结构的，比如星系及其周围明显的不可见光晕，通常被称为暗物质光晕？我们回答这些问题的能力具体取决于将暗物质粒子的微观物理与比星系规模更大的结构形成的宏观物理联系起来：形成星系的暗物质光晕。星系和暗物质晕之间的动态被称为星系-晕连接。尽管预计星系将随后从暗物质晕中形成，但星系和晕之间的联系仍然没有被很好地理解。星系和暗物质晕之间的动态被称为星系-晕连接。利用计算机模拟，PI和一名实习生将与KIPAC主任兼斯坦福大学教员Risa Wechsler合作，深入了解对星系-晕连接的观测如何提供对特定暗物质模型的洞察。虽然暗物质有许多候选对象，但没有已知的和观察到的粒子可以充分解释暗物质晕圈和星系的形成。一种极有希望但仍是假设的粒子类型是一类被称为轴子类粒子(Alps)的粒子。直接探测实验并不是限制暗物质性质的唯一方法--观察暗物质有望在大范围内形成的结构是另一种方法。PI将首次使用模拟来测试阿尔卑斯山的微物理如何在晕占据分布函数上留下独特的印记，该分布函数描述了星系物质如何分布在整个暗物质晕中。我们的团队将模拟只由阿尔卑斯山组成的暗物质晕中星系的分布，以强有力地预测只有阿尔卑斯山的晕所特有的独特性质。PI是轴子类粒子暗物质理论方面的专家，而主持人Risa Wechsler是光学中的计算宇宙学、星系-晕连接和观测宇宙学方面的专家。最初的步骤将包括用公开可用的数值宇宙学代码模拟玻色子暗物质场，该代码专门解释与轴子类暗物质相关的量子压力，并可用于模拟多个亚晕--与卫星星系相关--围绕一个中心势--大质量中央星系--的相互作用。这一奖项反映了美国国家科学基金会的法定任务，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。

Understanding the formation of large-scale structures is one of the most challenging tasks in both observational and theoretical cosmology. When and how did particles -- as we understand them today -- come into existence? How did these particles then go on to produce the large-scale structures familiar from astronomical observations, such as galaxies and the apparent invisible halos around them, commonly called dark matter halos? Our capacity to answer these questions specifically depends on linking the microphysics of dark matter particles to the macrophysics of structure formation at scales larger than galaxies: the dark matter halos in which galaxies form. The dynamic between galaxies and dark matter halos is known as the galaxy-halo connection. Although it is expected that galaxies will subsequently form out of dark matter halos, the galaxy-halo connection is still not well understood. The dynamic between galaxies and dark matter halos is known as the galaxy-halo connection. Using computer simulations, the PI and a trainee will work with KIPAC director and Stanford faculty member Risa Wechsler to produce insights into how observations of the galaxy-halo connection can provide insight into specific dark matter models.While there are many candidates for dark matter, there is no known and observed particle that can adequately explain how dark matter halos and therefore galaxies, form. One extremely promising, yet still hypothetical particle type is a class known as axion-like particles (ALPs). Direct detection experiments are not the only way to constrain the properties of dark matter -- looking at the structures dark matter is expected to form on large scales is another way. The PI will use simulations to test, for the first time, how the microphysics of ALPs leave a unique imprint on the halo occupation distribution function, which describes how galactic matter is distributed throughout the dark matter halo. Our team will simulate the distribution of galaxies in a dark matter halo made only of ALPs to make strong predictions of distinct properties unique to ALP-only halos. The PI is an expert on axion-like particle dark matter theory, while host Risa Wechsler is an expert on computational cosmology, the galaxy-halo connection, and observational cosmology in the optical. Initial steps will include simulations of a boson dark matter field with a publicly available numerical cosmology code that specifically accounts for the quantum pressure associated with axion-like dark matter and can be used to simulate the interactions of multiple subhalos -- correlated with satellite galaxies -- orbiting one central potential, the massive central galaxy.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.