The Time Variability and Duty Cycle of Active Galactic Nuclei During Quenching

像银河系这样的星系正在稳定地形成恒星，但这样的星系最终会结束恒星的形成并“熄灭”。恒星如何在星系中形成的物理驱动因素尚不清楚，但在大质量星系中心发现的超大质量黑洞可能起着关键作用。该项目将使用星系中心超大质量黑洞照亮区域的时变辐射示踪剂来研究对最近结束恒星形成的星系的影响。该项目将为当前和不久的将来的设施，如JWST， 20-40米地面望远镜和下一代甚大阵列（ngVLA），了解在更远距离发现的星系提供关键的背景。该项目包括伊利诺斯大学天文学夏令营项目的开发和实施时间。这个夏令营针对的是10-12年级的女生，不过任何性别的学生都可以申请。我们将设计并实施学生利用时间序列数据探索变化天空的活动，探索目标设定方法。星系从恒星形成到静止的演化对观测到的星系群的建立至关重要。越来越多的证据表明，许多星系，特别是在高红移的星系，在快速变化的时期经历了这种转变。来自活动星系核（AGN）的反馈可以提供足够的能量来结束恒星的形成，但AGN活动的作用及其结束恒星形成的机制仍然不确定。我们建议使用在低红移下确定的星暴后星系作为实验室，研究AGN反馈如何以及何时可能起作用。这些星系最近经历了恒星形成的爆发，在过去的10亿年内突然结束，类似于在高红移的大质量静止星系中看到的戏剧性的熄灭。由于许多常用的AGN示踪剂的不确定性以及AGN固有的变异性，在星爆后阶段AGN活性难以测量。pi将使用对一系列时间尺度敏感的示踪剂研究星爆后阶段AGN活动的存在。他们将使用档案和目标光学和无线电观测来研究周-年时间尺度上的光学变异性，年-几十年时间尺度上的无线电变异性，以及使用扩展电离区域在10,000-100,000年期间的极端状态变化。他们的结果将为未来观测更高红移演化星系提供关键的背景，为此，该团体将很快获得JWST和20-40米地面望远镜的深度静息框架光学光谱，以及ngVLA的冷分子气体测量。利用多波长的时域观测将使星系演化领域能够最大限度地提高Astro2020年十年调查报告中建议的时域天体物理学投资的科学回报。该奖项反映了美国国家科学基金会的法定使命，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。

Galaxies like the Milky Way are steadily forming stars, yet such galaxies will eventually end star formation and "quench". The physical drivers of how star formation ends in galaxies are not well understood, but the supermassive black holes that are found in the centers of massive galaxies may play a key role. The project will use tracers of time-variable emission from the areas illuminated by central supermassive black holes in galaxies to study the impact on galaxies which have recently ended star formation. The project will provide crucial context for understanding the galaxies discovered at larger distances with current and near-future facilities such as JWST, 20-40 meter ground-based telescopes, and the next-generation Very Large Array (ngVLA). The project includes time spent developing and implementing programs for the University of Illinois Astronomy summer camp. This camp is aimed at girls in grades 10-12, though students of any gender can apply. We will design and implement activities for students to explore the changing sky with time-series data to explore goal-setting methods.The evolution of galaxies from star-forming to quiescent is fundamental to the build-up of the observed galaxy population. There is growing evidence that many galaxies, especially at high redshift, experience this transition during a period of rapid change. Feedback from Active Galactic Nuclei (AGN) can provide enough energy to end star formation, yet the role of AGN activity and the mechanisms by which it can end star formation remain uncertain. We propose to use post-starburst galaxies identified at low redshift as laboratories for studying how and when AGN feedback might act. These galaxies have experienced recent bursts of star formation that have ended suddenly within the last billion years, analogous to the dramatic quenching seen in high redshift massive quiescent galaxies. AGN activity is difficult to measure during the post-starburst phase due to the uncertain nature of many commonly-used AGN tracers as well as the inherent variability of AGN. The PIs will study the presence of AGN activity during the post-starburst phase using tracers sensitive to a range of timescales. They will use archival and targeted optical and radio observations to study optical variability on timescales of weeks-years, radio variability on timescales of years-decades, and extreme changes in state over periods of 10,000-100,000 years using extended ionized regions. Their results will provide crucial context for future observations of higher redshift evolving galaxies, for which the community will soon obtain deep rest-frame optical spectroscopy with JWST and 20-40m ground-based telescopes, and cold molecular gas measurements with the ngVLA. Utilizing time-domain observations in multiple wavelengths will allow the field of galaxy evolution to maximize the scientific return on the investment in time domain astrophysics recommended in the Astro2020 decadal survey report.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.