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，根据标准宇宙学模型，通过观察宇宙最初数十万年发生的现象，目前宇宙的膨胀速度与预测的速度不一致。如果预测和测量之间的冲突被证实，没有任何合理的怀疑，那么标准的宇宙学模型将是不正确的，因此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宇宙当前膨胀速度的最精确测量，该项目将使用一种名为“引力时间延迟”的技术，这是合作团队在过去20年中开发的。测量结果将决定这种冲突是否真实存在，以及是否需要新的物理原理。该方案的更广泛影响将通过一个全面的教育/公共宣传部分来实现，目的是宣传研究的内容以及科学方法的重要性和意义。该计划包括在高中、本科生和研究生阶段教授科学研究基础，以及在NSF资助的CALBRIDGE计划的背景下指导本科生。宇宙微波背景测量值与宇宙H0膨胀率的局域测量之间8%的偏差表明，标准宇宙学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的物理学的发现，比如不是宇宙常数的暗能量，或者是额外的相对论物种家族。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。该计划将分三步进行。首先，时间延迟将被用来测量绝对宇宙距离，从而测量宇宙学参数。通过PIS团队开发的最先进技术，已经证明只需四个透镜就足以以3%的精度测量H0。其次，团队将进行后续(包括高分辨率成像、深部光谱和专用望远镜通道的监测)，并对他们最近发现的透镜进行建模，以进一步提高精度。第三，该计划将通过开发工具、进行模拟和数据挑战，为大天文观测望远镜时代的时延宇宙学奠定基础，最终目标是达到低于10%的精确度和准确度。该奖项反映了NSF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。

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.