WoU-MMA: Gravitational Lensing of Photons and Gravitational Waves in the Era of Multi-Messenger Astrophysics

该奖项支持相对论和相对论天体物理学的研究，并解决了NSF“宇宙之窗”大理念的优先领域。该奖项支持一项综合研究计划，以调查爱因斯坦广义相对论的三个壮观预测的汇合：引力透镜，黑洞（BH）和引力波（GW）。 引力透镜现象发生在前景物体（如星系或星系团）的引力场使背景源发射的辐射在向观察者传播时弯曲的时候。 黑洞是一种非常紧凑的大质量物体，它们拥有一个事件视界，甚至光也无法从其中逃逸。 引力波是时空结构中的涟漪，当物体穿过时，它会对物体施加随时间变化的潮汐力。 这项研究计划将研究引力透镜如何影响遥远的双星BH及其周围气体发出的GW和电磁（EM）辐射。 它有三个主要目标：（1）确定GW源被透镜化的概率以及透镜化放大和失真的强度，（2）评估透镜化是否可以在观测上与背景源的性质的内在变化区分开，以及（3）识别如何联合（多信使）引力透镜的GW和EM观测可以揭示前景透镜，背景源，以及引力透镜现象本身，这将是无法单独进行GW或EM观测的。 这项研究将通过显著推进对引力透镜作为一种多信使现象的理解来促进科学的进步。这项研究计划还将通过支持教育和公共宣传来造福社会。 它将资助两名研究生在物理学博士课程在得克萨斯大学达拉斯（UTD）的研究助学金，并提供本科生研究的机会。 爱因斯坦的遗产（特别是本提案中的研究主题）一直吸引着公众，因此成为向代表性不足的群体进行宣传的宝贵工具。 该团队将向不同的观众展示这项研究，包括达拉斯ISD的TAG Magnet学校，UTD Women in Physics夏令营，德克萨斯州业余天文学家天文学会，以及达拉斯的Frontiers of Flight和Perot博物馆。当前和未来的GW探测器将观察三类源：（1）像LIGO/Virgo所看到的那样的恒星质量双星BH合并，（2）超大质量黑洞（SMBH）合并，这是丽莎的主要目标，（3）紧凑物体到SMBH的极端质量比吸气（EMRI）。 拟议的研究将在三个相互关联的项目中调查这些来源的强引力透镜。(1)PI的小组将计算宇宙学红移源的透镜放大因子的分布，适当地使用波动或几何光学。 然后，他们将使用这个分布来确定透镜效应对三个GW源的影响有多强，包括信噪比的变化以及与用于搜索的未透镜GW模板的不匹配。 (2)该团队将探索引力透镜和定义非透镜波形的源参数变化之间的简并性。 特别是，他们将确定由于未对准的自旋引起的GW幅度调制可以模拟多个图像之间的干涉的程度，以及波形倾斜和偏振角的变化是否可以与具有不同偏振角和奇偶校验的透镜图像的相干总和区分开。 (3)该小组将研究强透镜系统的GW和EM观测之间的协同作用。 这项研究将解决即将到来的EM调查，如LSST，是否可以提供目录，以帮助确定主星系的透镜GW事件，如果透镜重建从EM观测可以帮助确定时间延迟的“图像”在GW数据，以及EM和GW的联合观测是否可以改善对透镜和源模型的约束。该奖项反映了NSF的法定使命，并通过使用基金会的学术价值和更广泛的影响审查标准。

This award supports research in relativity and relativistic astrophysics and it addresses the priority areas of NSF's "Windows on the Universe" Big Idea. This award supports an integrated research program to investigate the confluence of three spectacular predictions of Einstein’s theory of general relativity: gravitational lensing, black holes (BHs), and gravitational waves (GWs). Gravitational lensing occurs when the gravitational field of a foreground object like a galaxy or galaxy cluster bends the path of radiation emitted by a background source as it travels towards the observer. BHs are massive objects so compact that they possess an event horizon from within which even light cannot escape. GWs are ripples in the fabric of spacetime that exert time-varying tidal forces on objects as they pass through them. This research program will investigate how gravitational lensing affects the GWs and electromagnetic (EM) radiation emitted by distant binary BHs and their surrounding gas. It has three main goals: (1) to determine the probability that GW sources are lensed and the strength of lensing magnification and distortion, (2) to assess whether lensing can be observationally distinguished from intrinsic changes to the properties of the background sources, and (3) to identify how joint (multi-messenger) GW and EM observations of gravitational lensing can reveal properties of the foreground lenses, background sources, and the lensing phenomenon itself that would be inaccessible to GW or EM observations individually. This research will promote the progress of science by significantly advancing the understanding of gravitational lensing as a multi-messenger phenomenon. This research program will also benefit society by supporting education and public outreach. It will fund research assistantships for two graduate students in the physics PhD program at the University of Texas at Dallas (UTD) and also provide opportunities for undergraduate research. Einstein’s legacy (especially the research topics in this proposal) has always fascinated the public and thus serves as a valuable tool for outreach to underrepresented groups. The team will present this research to diverse audiences including the TAG Magnet School in Dallas ISD, the UTD Women in Physics summer camp, the Texas Astronomical Society of amateur astronomers, and the Frontiers of Flight and Perot museums in Dallas.Current and future GW detectors will observe three classes of sources: (1) stellar-mass binary BH mergers like those seen by LIGO/Virgo, (2) supermassive black-hole (SMBH) mergers that are the primary target of LISA, and (3) extreme-mass-ratio inspirals (EMRIs) of compact objects into SMBHs. The proposed research will investigate strong gravitational lensing of these sources in three interrelated projects. (1) the PI's group will calculate the distribution of lensing amplification factors for sources at cosmological redshift, using wave or geometric optics as appropriate. They will then use this distribution to determine how strong lensing affects the three GW sources including the changes to the signal-to-noise ratio and the mismatch with the unlensed GW templates used for searches. (2) The team will explore the degeneracies between gravitational lensing and changes to the source parameters that define unlensed waveforms. In particular, they will determine the extent to which GW amplitude modulation due to misaligned spins can mimic the interference between multiple images, and whether changes to the waveform inclination and polarization angle can be distinguished from the coherent sum of lensed images with different polarization angles and parities. (3) The group will investigate the synergy between GW and EM observations of strongly lensed systems. This study will address whether upcoming EM surveys like LSST can provide catalogs to help identify the host galaxy of lensed GW events, if lensing reconstruction from EM observations can help identify time-delayed “images” in GW data, and whether combined EM and GW observations can improve the constraints on lens and source models.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.