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”。恒星形成如何在星系中结束的物理驱动因素还不是很清楚，但在大质量星系中心发现的超大质量黑洞可能起到关键作用。该项目将使用星系中心超大质量黑洞照射区域的时变发射示踪剂来研究对最近结束恒星形成的星系的影响。该项目将为理解利用JWST、20-40米地面望远镜和下一代甚大阵列(NgVLA)等现有和近期设施在更远距离发现的星系提供关键背景。该项目包括为伊利诺伊大学天文学夏令营开发和实施项目所花费的时间。这个夏令营面向10-12年级的女孩，但任何性别的学生都可以申请。我们将设计和实施活动，让学生利用时间序列数据探索变化的天空，以探索设定目标的方法。星系从恒星形成到静止的演化是建立观测到的星系群的基础。越来越多的证据表明，许多星系，特别是高红移星系，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活动的作用和结束恒星形成的机制仍然不确定。我们建议使用低红移的恒星爆炸后星系作为实验室，研究活动星系核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10亿年里突然终止，类似于高红移大质量静止星系的戏剧性猝灭。由于许多常用的活动星系核示踪剂的不确定性以及活动星系核本身的变异性，在恒星爆发后阶段很难测量活动星系核的活动。PIS将使用对一系列时间尺度敏感的示踪剂来研究恒星爆发后阶段活动星系核的存在。他们将利用档案和有针对性的光学和射电观测，研究数周至数年时间尺度上的光学可变性，数年至数十年时间尺度上的射电可变性，以及使用扩展电离区的10,000-100,000年期间状态的极端变化。他们的结果将为未来对红移更高的演化星系的观测提供关键的背景，为此，该社区将很快使用JWST和20-40米地面望远镜获得深度静止框架光学光谱，并使用ngVLA测量冷分子气体。利用多波长的时间域观测将允许星系演化领域最大限度地实现Astro2020十年十年调查报告中建议的时间域天体物理投资的科学回报。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。

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.