Collaborative Research: Disentangling the Cosmic Web with Fast Radio Bursts

多年来，天文学家一直试图理解和观察星系之间的弥漫气体，也被称为星系间介质（IGM），或者更通俗地说，宇宙网。加州大学圣克鲁斯分校（UCSC）和玛丽亚米切尔天文台（MMO）之间的一项研究合作将利用对最近发现的一种被称为快速射电暴（frb）的短天文事件的精确观测来调查并试图解开宇宙网。该项目将包括采集和分析100多个定位良好的快速射电暴的光学和红外后续观测数据，这些数据是通过领先的快速射电暴精确定位实验（ASKAP、realfast和DSA-110）发现的，然后用大口径望远镜进行观测。利用计划的数据集，天文学家将集中在三个主要活动上：(i)获得主办快速射电暴的星系的后续成像和光谱，（ii）解决本星系群中电离气体的分布，以及（iii）解开宇宙网。该项目将支持加州大学圣迭戈分校一名观测天文学全日制博士生的教育和培训。与此同时，MMO的桥梁项目将为来自代表性不足的社区的研究生提供机会，培养他们进入博士课程所需的技能（如编程、统计、观察）。现在，在宇宙尺度（~100 Mpc）上的数值模拟声称能够捕捉到准确预测IGM天体物理学所需的所有重要物理现象。这些模拟预测，大约50%的气体处于温热电离介质（WHIM）中，在坍缩成大型结构的过程中受到冲击加热。然而，尽管对WHIM进行了几十年的观测搜索，它仍然是宇宙中最难以捉摸的重子储存库。与此同时，在单个暗物质晕的尺度上（~100—1000kpc），理论学家对其中气体的质量和分布进行了争论。该项目将利用一个新的机会，通过对快速射电暴事件进行全面的观测调查，解开宇宙网的谜团。从上述三个观测活动中产生的三个主要研究领域是：(i)建立FRB红移，并为产生这些神秘现象的祖星系提供新的见解；（ii）利用观测到的快速射电暴色散测量进行一系列实验，旨在调查银河系和M31的光晕气体，同时寻找假定的本星系群介质；（iii）直接测试IGM（及其WHIM）的现代范式，并评估暗物质晕的重子部分作为其质量、形态和环境的函数。为了支持从快速射电暴观测中获得的更广泛的科学成果，该项目获得的所有数据将通过一个或多个渠道传播给社区。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。

For many years, astronomers have been trying to understand and observe the diffuse gas between galaxies, also known as the intergalactic medium (IGM) or -- more colloquially -- the cosmic web. A research collaboration between the University of California-Santa Cruz (UCSC) and the Maria Mitchell Observatory (MMO) will use precise observations of a recently discovered type of short astronomical event called fast radio bursts (FRBs) to investigate and attempt to disentangle the cosmic web. This project will involve the acquisition and analysis of optical and infrared follow-up observations of over 100 well-localized FRBs, discovered using the leading FRB experiments for precise localization (ASKAP, realfast, and DSA-110) and then observed with large aperture telescopes. Using the planned dataset, the astronomers will focus on three main activities: (i) obtain follow-up imaging and spectroscopy of the galaxies hosting FRBs, (ii) resolve the distribution of ionized gas in the Local Group of galaxies, and (iii) disentangle the cosmic web. The project will support the education and training of a full-time PhD student at UCSC in observational astronomy. The Bridge program at MMO, meanwhile, will provide postgraduate students from underrepresented communities the opportunity to build the skill set (e.g. programming, statistics, observing) needed to transition into a PhD program. Numerical simulations on cosmological scales (~100 Mpc) now purport to capture all of the salient physics required to accurately predict the astrophysics of the IGM. These simulations predict that about 50% of the gas is in a warm-hot ionized medium (WHIM), shock-heated during its collapse onto large-scale structures. Despite several decades of observational searches for the WHIM, however, it remains the most elusive baryonic reservoir of the universe. Meanwhile, on the scales of individual dark matter halos (~100 -- 1000 kpc), theorists debate on the mass and distribution of gas within them. The program will leverage a new opportunity to disentangle the cosmic web through a comprehensive, observational survey of FRB events. The three main research areas arising from the three observational activities listed above are: (i) establish the FRB redshift and provide new insights into the progenitors that generate these enigmatic phenomena; (ii) use the observed FRB dispersion measures to perform a series of experiments designed to survey the halo gas of our Galaxy and M31, while also searching for the putative Local Group medium; and (iii) directly test the modern paradigm for the IGM (and its WHIM) and assess the baryon fraction of dark matter halos as a function of their mass, morphology, and environment. To support the great breadth of science derived from FRB observations beyond the focus of the project, all of the data obtained with this program will be disseminated to the community through one or more channels.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.