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

WoU-MMA：多信使天体物理时代光子和引力波的引力透镜

• 批准号: 2011977
• 负责人: Michael Kesden
• 金额: $ 29.99万
• 依托单位: University of Texas at Dallas
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-05-15 至 2024-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2011977&HistoricalAwards=false
• 关键词: WoU; MMA; Gravitational; Lensing; Photons

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.

该奖项支持相对论和相对论天体物理学的研究，并阐述了美国国家科学基金会“宇宙之窗”宏伟构想的优先领域。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(BHS)和引力波(GWS)。当像星系或星系团这样的前景物体的重力场弯曲了背景源向观测者发射的辐射的路径时，引力透镜就会发生。黑洞天体是质量很大的天体，非常致密，它们拥有一个事件视界，在这个视界中，即使是光也无法逃脱。GW是时空结构中的涟漪，当物体穿过它们时，它们会对物体施加时变的潮汐作用力。这项研究计划将研究引力透镜如何影响遥远的双星黑洞及其周围气体发出的GWS和电磁(EM)辐射。它有三个主要目标：(1)确定GW源被透镜的概率以及透镜放大和失真的强度，(2)评估透镜是否可以从观测上与背景源特性的内在变化区分开来，以及(3)确定引力透镜的联合(多信使)GW和EM观测如何揭示前景透镜、背景源和透镜现象本身的特性，这些特性将是GW或EM观测无法单独获得的。这项研究将极大地促进对引力透镜这一多信使现象的理解，从而推动科学的进步。这项研究计划还将通过支持教育和公共宣传而造福社会。它将为德克萨斯大学达拉斯分校(UTD)物理学博士项目的两名研究生提供研究助学金，并为本科生提供研究机会。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，因此是接触代表不足群体的宝贵工具。该团队将向不同的观众展示这项研究，包括达拉斯ISD的TAG磁力学校，UTD女性物理夏令营，德克萨斯业余天文学会，以及达拉斯的飞行和佩罗博物馆前沿。目前和未来的GW探测器将观察到三类来源：(1)LIGO/Virgo看到的恒星-质量双星黑洞合并，(2)LISA的主要目标超大质量黑洞合并，以及(3)致密天体形成SMBH的极端质量比灵感(EMRI)。这项拟议的研究将在三个相互关联的项目中调查这些源的强引力透镜效应。(1)PI小组将使用适当的波光学或几何光学计算宇宙红移源的透镜放大因子的分布。然后，他们将使用这一分布来确定透镜对三个GW源的影响程度，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未透镜波形的源参数变化之间的简并。特别是，他们将确定由于自旋未对准而导致的GW幅度调制可以在多大程度上模拟多个图像之间的干扰，以及是否可以从具有不同偏振角和奇偶数的透镜图像的相干和中区分波形倾斜度和偏振角的变化。(3)该小组将研究GW和EM对强透镜系统的观测之间的协同作用。这项研究将讨论即将进行的EM调查(如LSST)是否能提供星表以帮助识别透镜状GW事件的宿主星系，EM观测的透镜重建是否有助于识别GW数据中的时间延迟“图像”，以及EM和GW观测的组合是否可以改善对透镜和震源模型的限制。这一奖项反映了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。