WoU-MMA: Multi-Messenger Gravitational Lensing with Asymmetric Lenses and Sources

该奖项涉及爱因斯坦广义相对论的三个壮观预测：黑洞(BHS)、引力波(GWS)和引力透镜。当像BHS这样的大质量致密天体由于它们之间的巨大引力而迅速相互轨道并合并时，它们会在时空-GWS中产生涟漪。这些GW在地球上被探测到，是像LIGO这样的探测器手臂长度的微小变化。BHS的质量、自转和轨道参数决定了观测到的GW信号的频率和幅度作为时间的函数。自2015年LIGO合作首次发现以来，已经观察到90多个双星致密天体合并。这打开了一扇令人兴奋的宇宙新窗口，补充了用望远镜捕捉电磁波(如光学光)所看到的东西。当GWS或EM波穿过宇宙时，它们可以通过非常接近其路径的大质量物体的介入而偏转和聚焦。虽然这种强烈的引力透镜现象还没有在GW源上被发现，但预计它会将GW信号分成多个放大的副本，每个副本都会走一条略有不同的路径到达观测者。在HST或JWST图像上看到的这种强烈透镜过程的EM模拟，是遥远的星系被前景星系团透镜拉伸成醒目的弧形。透镜信号依赖于介入透镜的重力，这使得它成为衡量和研究暗物质的重要工具。随着陆基GW探测器灵敏度的提高和LISA等天基探测器的出现，GW源将被观测到遥远的距离，在那里介入透镜的可能性相当大。这一奖项将增加我们对宇宙史上BHS的性质和引力的理解，以及暗物质在中间透镜中的分布。这将为GWS的强透镜效应提供新的理论模型。该奖项还将促进几项有益于社会的教育和外展活动，例如扩大互动活力(与引力波的虚拟相互作用以观察相对论)模拟双星黑洞，为当地高中和本科生班编制课程材料，以及与博物馆合作。研究生和本科生将沉浸在研究中，激励和培养学术界和工业界的下一代科学家。未来将观察到越来越多的高红移GW事件，其中很大一部分将经历强烈的引力透镜作用。目前的大多数研究都假定双黑洞(BBH)源关于其轨道角动量的轴对称，以及透镜模型关于从观察者通过透镜的光轴的轴对称。这些假设将在三个相互关联的项目中放松。(1)极端质量比激发(EMRI)的透镜，其中轨道角动量通常与超大质量黑洞(SMBH)自转不一致，并且透镜可能被误解为偏离广义相对论。(2)更真实的透镜模型的透镜放大系数，包括嵌入在银河系中心的SMBH，核心密度分布，以及透镜星系或外部切变中的不对称性。(3)源星系或瞬变的电磁观测与GW源之间的协同作用。同时表征GW源中的进动和透镜对于它们用作天体物理和引力探测器是至关重要的。更逼真的非对称透镜模型对于实际数据分析也是必不可少的，因为轴对称模型定性地不能考虑几何光学限制中的额外图像，并且在源平面的大部分上使用更复杂的波动光学是必不可少的。大多数BBH合并可能会缺乏短暂的EM同行，因此将需要将GW和EM调查相关联的多信使研究来确定宿主星系。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。

This award is concerned with three spectacular predictions of Einstein’s theory of general relativity: black holes (BHs), gravitational waves (GWs) and gravitational lensing. When massive compact objects such as BHs rapidly orbit each other and merge due to the huge gravitational force between them, they create ripples in space-time – GWs. These GWs are detected on earth as tiny changes in the lengths of the arms of a detector such as LIGO. The masses, spins, and orbital parameters of the BHs determine the observed frequency and amplitude of the GW signal as a function of time. Since the first detection by the LIGO collaboration in 2015, more than 90 binary compact-object mergers have been observed. This has opened an exciting new window on the Universe that complements what is seen using telescopes that capture electromagnetic (EM) waves such as optical light. When GWs or EM waves pass through the Universe they can be deflected and focused by intervening massive objects very close to their path. Although this strong gravitational lensing phenomenon has not yet been identified for GW sources, it is expected to split GW signals into multiple magnified copies, each taking a slightly different path to the observer. An EM analog of this strong lensing process, as seen on HST or JWST images, are the distant galaxies stretched into eye-catching arcs by foreground galaxy cluster lenses. Lensing signatures depend on the gravity of the intervening lens, making it an essential tool to weigh and study dark matter. With the increasing sensitivity of ground-based GW detectors and the advent of space-based detectors like LISA, GW sources will be seen to vast distances where the chance of an intervening lens is considerable. This award will increase our understanding of the properties and gravity of BHs across cosmic history, and the distribution of dark matter in intervening lenses. It will provide new theoretical models of strong lensing of GWs. The award will also facilitate several educational and outreach activities of benefit to society, such as an extension of the interactive VIGOR (Virtual Interaction with Gravitational Waves to Observe Relativity) simulation of binary black holes, development of curriculum materials for local high schools and undergraduate classes, and engagement with museums. Graduate and undergraduate students will be immersed in the research, inspiring and training the next generation of scientists for academia and industry. Increasing numbers of high-redshift GW events will be observed in the future, and a significant fraction of these sources will experience strong gravitational lensing. Most current research assumes axisymmetry in both the binary black hole (BBH) sources about their orbital angular momentum and in the lens models about the optical axis passing from the observer through the lens. These assumptions will be relaxed in three interrelated projects. (1) Lensing of extreme-mass-ratio inspirals (EMRIs) in which the orbital angular momentum is generically misaligned with the supermassive black hole (SMBH) spin, and where lensing could be misinterpreted as deviations from general relativity. (2) Lensing amplification factors for more realistic lens models that include embedded SMBHs at galactic centers, cored density profiles, and asymmetry in either the lens galaxy or an external shear. (3) Synergies between EM observations of source galaxies or transients, and GW sources. Simultaneously characterizing precession and lensing in GW sources is critical for their use as probes of both astrophysics and gravity. More realistic asymmetric lens models are also essential for real data analysis, as axisymmetric models qualitatively fail to account for additional images in the geometric-optics limit and employing more complicated wave-optics is essential over much of the source plane. Most BBH mergers will probably lack transient EM counterparts, so multi-messenger studies correlating GW and EM surveys will be required to identify host galaxies.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.