From One to Many: Statistical Gravitational-Wave Astrophysics and Cosmology

2015年，引力波的发现，时空结构中的涟漪，让科学界兴奋不已，并被授予诺贝尔奖。科学家们现在经常探测中子星和/或黑洞碰撞产生的引力波。一份50宗此类合并的目录已经完成，预计未来几年还会有数百宗。这个项目将分析这个不断增长的星表，并确定属性的分布，如黑洞的质量和自转以及它们的距离。通过分析所有这些信息，就有可能推断出关于黑洞最初是如何形成的重要见解。黑洞的形成尤其令人着迷，因为它与恒星的死亡有关，因为黑洞被认为是由垂死的恒星形成的。更有趣的是，最近发现的大黑洞，其中一些质量远远超过太阳质量的50倍，与超大恒星的死亡有关--这些恒星被特别认为是最早和最原始的恒星之一。简而言之，通过研究黑洞碰撞，这项研究将了解宇宙中的第一批恒星，从而了解宇宙产生恒星、星系、元素，最终形成地球和地球上一切事物的过程。除了产生重要而新颖的科学外，这一提议还将向更广泛的公众传达该领域的一些美丽和兴奋之处，从小学生到老年人。蓬勃发展的事件目录使一种全新的方法能够从引力波源阐明科学：从检测到的引力事件总数进行统计推断。这个项目将通过建立工具和分析管道来回答一些与LIGO源有关的最令人兴奋的天体物理问题，从而推动引力波群体天体物理学领域的发展。具体的研究项目将包括描述质量间隙、自旋和质量比分布，以及探测到的群体的红移演化。这些结果将为双星系统的天体物理形成通道提供约束。对于小样本，每个事件在某种意义上都是一个“异常值”；随着人口的增长，PI将探索异常值和子总体之间的关键天体物理相关性。此外，PI还将探索中子星状态方程上的布居限制，并通过双星-主机连接进一步发展一种新的双星形成物理和天体物理探测器。这项研究将继续开发标准警报器，作为唯一干净和强大的宇宙学探测器，包括扩展对应和统计标准警报器的限制，并改进管道，并为在LIGO/处女座O4观测科学运行中刺激标准警报源的可能性做准备。工作还将包括进一步开发标准警报器科学的新方法，包括探索质量间隙宇宙学。该项目将使用质量分布的上边和下边作为观测“特征”，以提供宇宙膨胀历史对非常高的红移的独立约束。随着引力波探测的数量继续突飞猛进，事件的统计特征将提供重要的见解，这项工作将有助于为人口引力波天体物理学和宇宙学铺平道路。这一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 2015 discovery of gravitational waves, ripples in the fabric of space and time, electrified the scientific community and was awarded the Nobel Prize. Scientists are now routinely detecting gravitational waves from the collisions of neutron stars and/or black holes. A catalog of 50 such mergers has been assembled, with hundreds more expected in the coming years. This project will analyze this growing catalog, and determine the distribution of properties such as the mass and spin of the black holes as well as their distances. By analyzing all of this information, it is possible to infer important insights about how the black holes were formed in the first place. And the formation of black holes is particularly fascinating because it relates to the deaths of stars, since black holes are thought to be formed from dying stars. Even more interesting, the recent detections of big black holes, some of them well over 50 times the mass of our Sun, are related to the deaths of very big stars—these are specifically thought to be some of the earliest and most pristine stars. In short, by studying black hole collisions, this study will learn about the first stars in the Universe, and therefore the process by which the Universe makes stars, galaxies, the elements, and eventually, the Earth and everything on it. In addition to producing important and novel science, this proposal will also convey some of the beauty and excitement of the field to the broader public, ranging from primary school students through to senior citizens.The burgeoning catalog of events enables an entirely new approach to elucidating science from gravitational-wave sources: statistical inference from the detected population of gravitational events. This project will advance the field of gravitational-wave population astrophysics by building the tools and analysis pipelines to answer some of the most exciting astrophysical questions related to LIGO sources. Specific research projects will include characterizing mass gaps, spin and mass ratio distributions, and the redshift evolution of the detected population. These results will inform constraints on the astrophysical formation channels of binary systems. For small samples, every event is in some sense an “outlier”; as the population grows, the PI will explore the critical astrophysical relevance of outliers and sub-populations. In addition, the PI will explore population constraints on the neutron star equation of state, and further develop a novel probe of binary formation physics and astrophysics through the binary-host connection. The study will continue to develop standard sirens as uniquely clean and powerful cosmological probes, including extending counterpart and statistical standard sirens constraints, and refining pipelines and preparing for the possibility of exciting standard siren sources in the LIGO/Virgo O4 observational science run. Work will also include further development of novel approaches to standard siren science, including the exploration of mass-gap cosmology. The project will use the upper and lower edges of the mass distribution as observational “features” to provide independent constraints of the expansion history of the universe to very high redshift. As the number of gravitational-wave detections continues to grow by leaps and bounds, statistical characterization of the events will provide important insights, and this work will help pave the way for population gravitational-wave astrophysics and cosmology.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.