Hunting for Black Holes with Astrometric Microlensing

黑洞是天体物理学中最奇特的现象之一，也是最基本的物理学：引力和量子力学得到检验的地方。银河系可能包含1000万到10亿个恒星质量的黑洞：那些质量比太阳大几倍的黑洞。 估计这个数字和黑洞质量的真实分布可以提供黑洞如何形成的重要约束，早期宇宙中原始黑洞的存在，以及最近引力波探测合并黑洞对的解释。到目前为止，还没有发现孤立的恒星质量黑洞，只有几十个黑洞测量了质量-所有都是双星。 微透镜效应是广义相对论的一种效应，黑洞的引力使从地球上观察到的背景星星的光线成为透镜，它提供了一种检测孤立黑洞并测量其质量的方法。 加州大学伯克利分校的一个研究小组将对微透镜事件进行敏感的观测，以测量放大的亮度和偏移的天体测量位置，使他们能够精确测量透镜物体的质量，并确定它是否确实是一个黑洞或仅仅是两颗正常恒星之间的偶然透镜事件。 这一结果预计将是对银河系中孤立黑洞的第一次明确探测。 作为该项目的一部分，首席研究员还将通过改善对教师的培训来加强下一代科学家和工程师的培训和多样性。PI将启动U。C.科学家和工程师教育家研究所的伯克利分会，提供专业发展计划，使初级研究人员能够接受基于探究的教学方法和教育教学法的培训。 因此而开展的新的调查活动也将免费传播给广大的天文学家社区，以扩大该计划的影响。该项目旨在开发一种新的高精度天体测量实验，以观测长时间的微透镜事件，并首次探测和测量孤立黑洞的质量。 利用自适应光学系统在W. M.在凯克天文台，将监测大约7个长持续时间微透镜事件（即候选黑洞）的样本，以测量它们的透镜质量。对于10个太阳质量的黑洞，透镜质量的预期精度为~10%，预测的黑洞探测率为~ 50%。由此产生的黑洞探测频率和质量从拟议的调查将被用来限制在银河系中的黑洞，它们的二进制分数，和踢速度的总数。找到这些孤立的黑洞将减少银河系中黑洞总数的数量级不确定性，并限制黑洞形成和演化的理论。天体测量微透镜所需的天体测量技术的拟议发展也将为天体物理学许多领域的新探索奠定基础。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。

Black holes are one of the most exotic phenomena in astrophysics and are places where the most fundamental physics: gravity and quantum mechanics are tested. The Milky Way Galaxy likely contains between ten million and a billion stellar-mass black holes: those with masses a few times larger than the Sun. Estimating this number and the true distribution of black hole masses can provide important constraints on how black holes form, the existence of primordial black holes from the early universe, and the interpretation of recent gravitational wave detections of merging black hole pairs. To date, no isolated stellar-mass black holes have been definitively detected and only a few dozen black holes have measured masses -- all in binaries. Microlensing, an effect of general relativity where a black hole's gravity lenses the light of a background star observed from Earth, provides a method to detect isolated black holes and measure their masses. A research team at the University of California-Berkeley will carry out sensitive observations of microlensing events to measure both the magnified brightness and the shifted astrometric position, allowing them to precisely measure the mass of the lensing object and determine if it is indeed a black hole or simply a chance lensing event between two normal stars. The outcome is expected to be the first unambiguous detection of an isolated black hole in the Milky Way. As part of the project, the principal investigator (PI) will also enhance the training and diversity of the next generation of scientists and engineers by improving the training for the teachers who will educate them. The PI will start a U. C. Berkeley chapter of the Institute for Scientist and Engineer Educators, which provides a professional development program that enables junior researchers to receive training in inquiry-based teaching methods and education pedagogy. New inquiry activities developed as a result will be also freely disseminated to a broad community of astronomers to multiply the impact of the program.This project aims to develop a new high-precision astrometry experiment to observe long-duration microlensing events and detect and measure the masses of isolated black holes for the first time. Using astrometric observations obtained from the adaptive optics system on the W. M. Keck Observatory, a sample of approximately seven long-duration microlensing events (i.e. candidate black holes) will be monitored in order to measure their lens masses. The expected accuracy on the lens mass is ~10% for a ten solar mass black hole and the predicted black hole detection rate is ~50%. The resulting black hole detection frequency and masses from the proposed survey will be used to constrain the total number of black holes in the Galaxy, their binary fraction, and kick velocities. Finding these isolated black holes would reduce the orders of magnitude uncertainty on the total number of black holes in the Galaxy and constrain theories of black hole formation and evolution. The proposed development of astrometry techniques, needed for astrometric microlensing, will also lay a foundation for new explorations in many areas of astrophysics.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.