Towards Robust Measurements of H0 with Dark Standard Candles

使用深色标准烛光对 H0 进行稳健测量

• 批准号: 2307026
• 负责人: Dragan Huterer
• 金额: $ 64.74万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2307026&HistoricalAwards=false
• 关键词: Towards; Robust; Measurements; H0; Dark

Measurements of the expansion rate of the universe -- the Hubble constant -- have historically been uncertain, but have in the past two decades converged to the concordance value. However, a major recent development in cosmology has been the disagreement between the Hubble constant determinations by two major cosmological probes. Namely, the precision (indirect) measurement of the Hubble constant by the cosmic microwave background anisotropies gives a much lower value for the expansion rate than the direct determination from nearby galaxies and type Ia supernovae. The two measurements are mutually inconsistent at the "five sigma" level, corresponding to confidence of about 99.9999%. Search for the explanation of this so-called Hubble tension has become a central effort in cosmology. Scientists at the University of Michigan and the University of Pennsylvania propose to dramatically improve the reliability of an alternative method to measure the Hubble constant, which has the power to shed new light or outright resolve the Hubble tension. This method utilizes the so-called ``dark standard siren'' gravitational-wave events. As part of this project, the team will also engage in a number of outreach activities, including running an annual summer course for high-school students and organizing the biannual Cosmology Summer School (at Michigan); as well as organizing lectures during AstroFest and running the Neighborhood Workshop on Astrophysics and Cosmology (at Penn State).Standard sirens are mergers that result in observed gravitational-wave signatures whose wave-forms provide distances to these events. The dark sirens are those events in which the electromagnetic counterpart is not discovered (and the corresponding redshift not measured), complicating the consequent determination of the Hubble constant. The team will study how the cross-correlation between galaxies and gravitational-wave dark sirens can be used to measure the Hubble constant. This cross-correlation approach should allow a much cleaner separation of the cosmological signal from biases that are due to a variety of systematic errors, but can also be purely statistical. The team will thoroughly test this method against the systematic errors, then apply it to current data, and identify prospects for Hubble-constant constraints with future data. Finally, the team will also investigate the effect of astrophysical systematics on the ability to recover the Hubble constant.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.

宇宙膨胀率的测量——哈勃常数——在历史上一直是不确定的，但在过去的二十年里已经收敛到了一致性值。然而，宇宙学最近的一个重大发展是两个主要宇宙学探测器对哈勃常数的测定之间存在分歧。也就是说，通过宇宙微波背景各向异性对哈勃常数的精确（间接）测量给出的膨胀率值比从附近星系和Ia型超新星直接确定的值要低得多。两个测量值在“5 sigma”水平上相互不一致，对应的置信度约为 99.9999%。寻找这种所谓的哈勃张力的解释已成为宇宙学的核心工作。密歇根大学和宾夕法尼亚大学的科学家提议大幅提高测量哈勃常数的替代方法的可靠性，该方法有能力揭示新的线索或彻底解决哈勃张力。这种方法利用了所谓的“暗标准警报”引力波事件。作为该项目的一部分，该团队还将参与一系列外展活动，包括为高中生举办一年一度的暑期课程，以及组织一年两次的宇宙学暑期学校（在密歇根州）；以及在 AstroFest 期间组织讲座并举办天体物理学和宇宙学邻里研讨会（宾夕法尼亚州立大学）。标准警报器是合并，导致观测到的引力波特征，其波形提供了到这些事件的距离。暗警报是那些没有发现电磁对应物（并且没有测量相应的红移）的事件，使哈勃常数的后续确定变得复杂。该团队将研究如何利用星系和引力波暗警报之间的互相关来测量哈勃常数。这种互相关方法应该可以更清晰地将宇宙学信号与由于各种系统误差引起的偏差分开，但也可以是纯粹的统计方法。该团队将针对系统误差彻底测试该方法，然后将其应用于当前数据，并确定未来数据的哈勃常数约束的前景。最后，该团队还将研究天体物理系统学对恢复哈勃常数的能力的影响。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。