Using a Uniform Sample of Sub-Galactic-Scale Binary Active Galactic Nuclei to Understand Changes in Galaxies Over Time Caused by Galaxy Merging

冷暗物质宇宙学的一个基本预测是，星系通过一系列与其他星系或大或小的合并而成长。通过详细的观测和理论模型来研究星系合并，我们可以了解星系随时间的变化。在过去的二十年中取得了重大进展，但问题远未解决。星系合并的关键物理过程仍然知之甚少。特别是，由于观测方面的挑战，模拟做出的预测到目前为止还难以确定，这阻碍了观测和模拟之间的直接比较。这一建议旨在通过消除观测障碍和在小物理尺度上表征双黑洞的频率来提高我们对合并引起的星系变化的理解。本提案将识别、确认和表征千帕秒尺度双活动星系核（agn）的样本。这是首次在275平方度的范围内，利用高分辨率的深射电和光学巡天系统地识别双星。这次搜索将使目前千秒级双agn的样本增加一个数量级。不受尘埃遮挡的影响，样本将涵盖宿主星系的一系列特性和黑洞的吸积模式。通过将统一选择的双agn与匹配的对照样本进行比较，研究小组将研究星系形成和变化的合并范式中的一些悬而未决的问题：合并能否触发并同步黑洞吸积？双吸积/反馈模式（辐射模式vs喷流模式）的起源是什么？AGN反馈能否在短时间尺度（~1,000,000年）内显著影响恒星形成活动？由于引力波反冲或双星形成的延迟，超大质量黑洞围绕恒星核心振荡的频率有多高？作为大质量黑洞双星的直接前身，千秒尺度星系合并的研究也将对低频引力波实验产生重要影响。

Part 1One of the fundamental predictions of the cold dark matter cosmology is that galaxies grow through a series of major and minor mergers with other galaxies. By studying galaxy mergers through detailed observations and theoretical models, we can understand galaxy changes over time in general. Significant progress has been made in the past two decades, but the problem is far from solved. The key physical processes of galaxy merging remain poorly understood. In particular, simulations make predictions that until now have been difficult to identify because of observational challenges, hindering direct comparison between observation and simulation. This proposal seeks to advance our understanding of galaxy changes caused by mergers by eliminating the observational obstacles and characterizing the frequency of binary black holes at small physical scales.Part 2This proposal will identify, confirm, and characterize a sample of kiloparsec-scale binary Active Galactic Nuclei (AGNs). For the first time, the binaries will be identified systematically using high-resolution deep radio and optical surveys in a 275 square degree field. This search will increase the current sample of kiloparsec-scale binary AGNs by an order-of-magnitude. Unbiased by dust-obscuration, the sample will cover a range of host galaxy properties and black-hole-accretion modes. By comparing the uniformly selected binary AGNs with matched control samples, the team will investigate a number of outstanding questions in the merger paradigm of galaxy formation and change: Can mergers trigger and synchronize black hole accretion? What is the origin of the two-accretion/feedback modes (radiative-mode vs. jet-mode)? Can AGN feedback significantly affect the star formation activity on a short timescale (~1,000,000 years)? How frequently does a supermassive black hole oscillate around a stellar core because of gravitational wave recoil or a delay in binary formation? As the immediate precursor of massive black hole binaries, studies of kiloparsec-scale galaxy mergers will also have important implications for low-frequency gravitational wave experiments.