Collaborative Research: Toward a 1% measurement of the Hubble Constant with gravitational time delays

近年来，高精度的测量使天文学家认识到，目前宇宙的膨胀速度与根据标准宇宙学模型通过观察宇宙最初几十万年发生的现象所预测的速度不一致。如果预测和测量之间的冲突被证实是毫无疑问的，那么标准的宇宙学模型将是不正确的，这将导致新的物理现象的发现，从而导致我们理解自然世界的方式的真正革命。为了独立于任何其他方法实现对当前宇宙膨胀速度的最精确测量，该项目将使用一种称为“引力时间延迟”的技术，这是合作团队在过去20年里开发的。测量结果将决定冲突是否真实，以及是否需要新的物理学。该项目的更广泛影响将通过全面的教育/公共宣传组成部分来实现，旨在传达研究内容和科学方法的重要性和意义。该项目包括在高中、本科和研究生阶段教授科学研究的基础，以及在美国国家科学基金会资助的CALBRIDGE项目的背景下指导本科生。宇宙微波背景测量值与当地对宇宙膨胀率的测定值之间8%的差异暗示，标准的宇宙模型可能并不完全准确。如果得到证实，这种差异可能会导致新物理学的发现，比如不是宇宙常数的暗能量，或者其他相对论性物种的家族。我们基于引力时间延迟的雄心勃勃的计划旨在实现迄今为止最精确的绝对距离测量，而不依赖于当地的距离阶梯。将实施一个三步走的方案。首先，时间延迟将用于测量绝对宇宙距离，从而测量宇宙参数。利用pi团队开发的最先进技术，仅用四个透镜就足以以3%的精度测量H0。其次，这些团队将对他们最近发现的透镜进行后续研究（包括高分辨率成像、深度光谱和专用望远镜监测）和建模，以进一步提高精度。第三，该项目将通过开发工具、开展模拟和数据挑战，为大型综合巡天望远镜时代的延迟宇宙学奠定基础，最终目标是达到亚百分之一的精度和准确度。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。

In recent years, high precision measurements have allowed astronomers to realize that the current expansion velocity of the Universe does not agree with the velocity predicted, on the basis of the standard cosmological model, by observing phenomena that have taken place in the first few hundred thousand years of the Universe. If the conflict between the prediction and the measurements is confirmed beyond any reasonable doubt, then the standard cosmological model would be incorrect, which would therefore lead to the discovery of new physical phenomena and thus to a true revolution in the way we understand the natural world. In order to achieve the most precise measurement of the current expansion velocity of the Universe independently of any other method, this project will use a technique called "gravitational time delays," which the collaborating teams have developed over the past twenty years. The measurement will determine whether the conflict is real and whether new physics is required. The broader impact of the program will be achieved through a comprehensive educational/public outreach component, aimed at communicating both the content of the research and the importance and significance of the scientific method. The program includes teaching the foundations of scientific research at the high-school, undergraduate, and graduate levels, as well as mentoring of undergraduate students in the context of the NSF-funded CALBRIDGE program. The 8% discrepancy between cosmic microwave background measurements and the local determination of the expansion rate of the Universe H0 hints that the standard cosmological model might not be entirely accurate. If confirmed, this discrepancy could lead to the discovery of new physics such as dark energy that is not the cosmological constant, or additional families of relativistic species. Our ambitious plan based on gravitational time delays aims to achieve the most precise absolute distance measurement to date, independent of the local distant ladder. A three-step program will be carried out. First, time delays will be used to measure absolute cosmic distances and thus cosmological parameters. With state-of-the art techniques developed by the PIs' teams, it has been shown that just four lenses are sufficient to measure H0 with 3% precision. Second, the teams will carry out follow-up (including high resolution imaging, deep spectroscopy and monitoring with dedicated telescope access) and modeling of lenses that they have recently discovered to further improve the precision. Third, the program will lay the foundations for time delay cosmology in the Large Synoptic Survey Telescope era by developing tools and carrying out simulations and data challenges with the ultimate goal of reaching sub-percent precision and accuracy.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.