Collaborative Research: WoU-MMA: The Benchmark Measurement of Quasar Spectroscopic Variability and Implications for Supermassive Black Hole Binaries and Changing-Look Quasars

大多数(如果不是全部)相当大质量的星系的中心都有超大质量黑洞，质量是太阳质量的数百万到数十亿倍。类星体是宇宙中最明亮的非爆炸物体，是气体坠落到这些超大质量黑洞上的结果，它们的亮度可以超过其所在星系中的所有恒星。它们之所以重要，是因为它们似乎在塑造星系今天的样子方面发挥了关键作用。然而，由于它们距离宇宙很远，它们在天空中看起来像针点般的光，我们不能在空间上分离黑洞周围的环境来研究它的特征。幸运的是，类星体本质上是可变的，亮度经常变化，这使得时域观测成为揭示其中央区域的强大工具，类似于使用电影来讲述故事，而不是一张照片。范德比尔特大学和宾夕法尼亚州立大学的研究团队将利用这些亮度变化和大数据技术来首次测量超大质量黑洞周围的气体如何在几年到十年的时间尺度上移动。这将使搜索奇异的来源成为可能，比如以前从未被探测到的双星系统中的超大质量黑洞(SBHB)，以及开启和关闭速度比理论解释得快得多的变化外观类星体(CLQ)。研究人员还将为Fisk-Vanderbilt Bridge项目的学生举办为期三天的数据挖掘研讨会，并使用流行的Zooniverse界面开发一系列天文学入门练习。该项目将构成对多年类星体光谱可变性的基准测量，并将其应用于搜索SBHBs和CLQs。这项工作将使用斯隆数字巡天的大约5000个类星体样本，这些类星体已经不止一次被光谱观测到，以测量宽广的H-β线的参数及其在1-18年的时间尺度上的变异性。这些将被用来定义规则类星体可变性的统计模型，适用于许多应用，包括搜索SBHBs和CLQs。利用该统计工具，该团队将(A)首次将SBHB候选与对照样本的总体可变性进行比较，(B)测试最佳亚PC分离SBHB候选的性质，(C)预测SBHB监测活动取得成果所需的持续时间，(D)限制SBHB候选可能具有的质量，(E)首次确定CLQ代表的是正常类星体可变性的极端例子还是明显的现象，和(F)严格和定量地定义CLQ类别。该奖项解决并推进了宇宙大理想之窗的目标。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。

Most, if not all, reasonably massive galaxies host supermassive black holes in their centers, with masses of millions to billions of times the mass of the Sun. The most luminous non-exploding objects in the Universe, quasars are the result of gas falling onto these supermassive black holes and they can outshine all of the stars in their host galaxy. They are important because they appear to play a key role in shaping how galaxies came to look the way that they do today. However, because of their large cosmological distances, they appear as pinpricks of light on the sky and we cannot spatially separate the environment around the black hole to study its characteristics. Fortunately, quasars are intrinsically variable with frequent changes in brightness, making time-domain observations a powerful tool in revealing their central regions, akin to using a movie to tell a story instead of a single photograph. The research team at Vanderbilt and Penn State Universities will leverage these brightness changes and big data techniques to make the first measurement of how gas around supermassive black holes moves over a timescale of years to a decade. This will enable searches for exotic sources, like supermassive black holes in binary (SBHB) systems which have never been detected before, and changing-look quasars (CLQs) which turn on and off much faster than theory can explain. The investigators will also conduct a three-day data mining workshop for students in the Fisk-Vanderbilt Bridge Program and develop a series of introductory astronomy exercises using the popular Zooniverse interface.This project will constitute the benchmark measurement of multi-year quasar spectroscopic variability and apply it to searches for SBHBs and CLQs. This work will use a sample of approximately 5000 quasars from the Sloan Digital Sky Survey that have been observed spectroscopically more than once to measure the parameters of the broad H-beta line and their variability over times scales of 1-18 years. These will be used to define a statistical model for regular quasar variability, appropriate for many applications, including searches for SBHBs and CLQs. With this statistical tool the team will (a) compare the ensemble variability properties of SBHB candidates to a control sample for the first time, (b) test the nature of the best sub-pc separation SBHB candidates, (c) predict the necessary duration for SBHB monitoring campaigns to bear fruit, (d) constrain the masses that SBHB candidates can have, (e) determine for the first time whether CLQs represent extreme examples of normal quasar variability or a distinct phenomenon, and (f) define the CLQ class rigorously and quantitatively.This award addresses and advances the goals of the 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.