WoU-MMA: Multi-messenger Titans: Probing The Dynamics & Environments Of Supermassive Binary Black Holes

现在我们知道，几乎每个星系的中心都有一个超大质量黑洞，其质量是太阳质量的数百万到数十亿倍。 如果一个超大质量黑洞处于一个致密的环境中，它可以通过落入其中的气体和尘埃发出的光来探测，这样的物体被称为活动星系核（AGN）。 人们还知道，这些巨大的物体中有一些是成对存在的，称为超大质量双黑洞（SMBBH），预计它们最终会螺旋形地相互碰撞，产生时空涟漪或引力波（GW）。 这些引力波会导致快速旋转的致密前恒星（称为恒星）的时间发生微小变化。 通过使用脉冲星定时阵列（PTA）中的多个射电望远镜测量这些时间变化，天文学家希望推断出这种GW的存在。 范德比尔特大学的一个研究小组将利用精密脉冲星定时阵列数据与活动星系核随时间变化的亮度和光谱的光学观测的合成，对SMBBH进行首次端到端相干多信使（MM）搜索。该项目产生的方法将预测2020年代第一次MM双星探测的预期特性，包括可能的双星环境和宿主星系特征。 调查人员还将建立一个天体物理学研究者学生团队（STARS）的范德比尔特节点，这是NANOGrav PTA团队建立的一个非常成功的国家计划。这项工作将涉及来自范德比尔特和菲斯克（附近一所历史悠久的黑人大学）的本科生，他们将直接参与脉冲星和引力波研究。该项目将打造一条路径，以明确识别SMBBH在sub-parsec分离，帮助解决这个迄今为止失踪的人口令人困惑的谜。虽然双活动星系核在千秒差距到七秒差距的距离上都被观测到，但在亚秒差距的距离上没有明确的SMBBH。一些候选的亚秒差距对已被确定为活动星系核中的准周期性光通量或径向速度变化，但这是严重阻碍的内在磁盘和环境噪声过程，可以模仿短基线的周期性行为。只有PTA数据可以直接推断SMBBH的存在，通过检测其~毫微微赫兹频率的GW。通过将PTA GW搜索与大型光度和光谱调查相结合，该项目将利用多个信使的力量来仲裁现有的候选者，预测第一个MM二进制检测的预期属性和限制，并将不同信使提供的信息融合到次秒差距的SMBBH动态的完整肖像中。这一提议代表了理解SMBBH的EM签名如何跟踪GW信号的巨大飞跃。 该项目推进了NSF宇宙大创意窗口的目标。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

It is now known that nearly every galaxy contains at its center, a supermassive black hole, with a mass millions to billions of times greater than the mass of the Sun. If a supermassive black hole is in a dense environment, it can be detected by the light emitted by gas and dust falling into it. Such an object is called an active galactic nucleus (AGN). It is also known that some of these titanic objects exist in pairs, called supermassive binary black holes (SMBBHs), which are expected to eventually spiral into each other and collide, producing ripples in spacetime, or gravitational waves (GWs). These GWs cause tiny variations in the timing of rapidly spinning compact former stars called pulsars. By measuring these timing variations using multiple radio telescopes in what is called a pulsar timing array (PTA), astronomers expect to infer the existence of such GWs. A research team at Vanderbilt University will perform the first end-to-end coherent multi-messenger (MM) search for SMBBHs using the synthesis of precision pulsar timing array data with optical observations of the time-varying brightness and spectra of AGN. The methods resulting from the project will forecast the expected properties of the first MM binary detection in the 2020s, including the likely binary environment and host galaxy characteristics. The investigators will also establish a Vanderbilt node of Student Teams of Astrophysics ResarcherS (STARS), a highly successful national program established by the NANOGrav PTA team. The work will involve undergraduate students from Vanderbilt and Fisk (a nearby historically black university), who will be directly involved in pulsar and gravitational-wave research. This project will forge a path to the unambiguous identification of SMBBHs at sub-parsec separations, helping to resolve the perplexing enigma of this heretofore missing population. While dual AGN have been observed at separations from kiloparsecs down to seven parsecs, there are no unambiguously identified SMBBHs at sub-parsec separations. Some candidate sub-parsec pairs have been identified as quasi-periodic optical-flux or radial-velocity variations in AGN, but this is severely hampered by intrinsic disk and environmental noise processes that can mimic periodic behavior over short baselines. Only PTA data can directly infer the presence of SMBBHs through detection of their ~nanohertz-frequency GWs. By combining PTA GW searches with large photometric and spectroscopic surveys, this project will leverage the strength of multiple messengers to arbitrate existing candidates, forecast the expected properties and constraints on the first MM binary detection, and fuse the information provided by different messengers into a complete portrait of SMBBH dynamics at sub-parsec separations. This proposal represents a dramatic leap forward in understanding how EM signatures of SMBBHs track the GW signal. This project advances the goals of the NSF Windows on the Universe Big Idea.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.