Counting the Unseen: Massive Black Hole Demographics from Tidal Disrution Events

过去二十年的重大科学发现之一是，大型星系和它们的中心超大质量黑洞（BH）一起演化，每一个都直接影响另一个的可观测性质。质量较小的星系是否也与中心黑洞共同进化，或者说，究竟有多少星系拥有中心黑洞，仍然是一个悬而未决的问题，因为很难探测到中等质量（10万太阳质量）的黑洞。一种很有前途的方法来探测和量化这些物体，利用潮汐破裂事件（TDE）期间发出的短暂爆发的光，其中BH的强大引力潮汐力将一颗离它太近的星星撕碎。该项目的主要目的是利用现有的颜色，恒星质量，和中心恒星密度测量的低质量星系在20百万秒差距，以模拟预期的频率和亮度的TDE，即将到来的维拉C。鲁宾天文台预计将探测到数千个。这些观测将揭示低质量星系中拥有黑洞的比例，它们的质量，以及更广泛的中央黑洞的主要形成机制。该项目将支持一个研究生以及本科生的外展实习生。而中等质量的黑洞是非常难以检测无论是运动学或通过其吸积签名，TDEs代表了一个强大的替代技术。然而，使用观测到的TDE来约束黑洞的“人口统计学”需要准确预测这些事件作为星系属性的函数。对于一阶，黑洞附近恒星的秒差距尺度密度是精确预测TDE速率的关键参数，而这样的空间尺度只能在~20 Mpc范围内旋转。在质量小于银河系的星系中，这些尺度上的中心密度（以及TDE率）由核星星团主导。该项目将使用核密度测量结合当今的恒星质量函数，以限制一系列BH质量分布和占用分数的TDE率。然后，这些预测可以与Zwicky Transient Factory（ZTF）和即将推出的Vera C的数据进行比较。鲁宾天文台首次确定了低至1亿太阳质量的星系中的BH人口统计。另外两个项目也将预测大质量星系周围剥离核中的TDE率，并试图解释星暴后星系中TDE的明显“过剩”（大约三分之一）。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

One of the major scientific discoveries of the last two decades is that large galaxies and their central super-massive black holes (BH) have evolved together, with each directly influencing observable properties of the other. Whether less massive galaxies have similarly coevolved with central BHs, or indeed, what fraction even possess them, is still an open question due to the difficulty in detecting intermediate mass (100,000 solar masses) BHs. A promising approach to detect and quantify these objects utilizes the brief outbursts of light emitted during a tidal disruption event (TDE), where a BH's strong gravitational tidal forces shred a star passing too close to it. The primary aim of this project is to use existing color, stellar mass, and central stellar density measurements of low mass galaxies within 20 Mpc to model the expected frequency and luminosities of TDEs that the upcoming Vera C. Rubin Observatory are expected to detect by the thousands. These observations will reveal the fraction of low-mass galaxies that host BHs, their masses, and more broadly the primary formation mechanism of central BHs. The project will support a graduate student as well as undergraduate outreach interns.Whereas intermediate mass BHs are exceedingly difficult to detect either kinematically or through their accretion signatures, TDEs represent a robust alternative technique. However, using observed TDEs to constrain black hole “demographics” requires accurate predictions of these events as a function of galaxy properties. To first order, the parsec scale density of stars in the immediate vicinity of a BH is the key parameter for accurately predicting TDE rates, and such spatial scales can only be revolved for galaxies within ~20 Mpc. In galaxies less massive than the Milky Way the central densities on these scales (and thus TDE rates) are dominated by nuclear star clusters. This project will use nuclear density measurements combined with present-day stellar mass functions to constrain the TDE rates for a range of BH mass distributions and occupation fractions. These predictions can then be compared to data from the Zwicky Transient Factory (ZTF) and the upcoming Vera C. Rubin Observatory to determine the BH demographics in galaxies as low as 100-million solar masses for the first time. Two additional projects will also predict TDE rates in stripped nuclei surrounding massive galaxies and attempt to explain the apparent “overabundance” (roughly one of every three) of TDEs in post-starburst 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.