标题： 通过中红外变异性量化宇宙空洞中的活动星系核比例 显示英文标题

标题： Quantifying the Active Galactic Nuclei Fraction in Cosmic Voids via Mid-Infrared Variability

摘要： 观测和理论模拟表明，大尺度环境在星系形成和演化中起着重要作用，特别是星系是否以及何时在其核心拥有一个正在吸积的超大质量黑洞（即活动星系核，或AGN）。AGN活动的一个特征是光度变化，当核周围尘埃重新处理AGN吸积盘发出的紫外线和光学光子时，会在中红外（中IR）出现这种变化。我们在这里通过使用AllWISE和NEOWISE的约12年综合多历元数据来量化中IR变化，提供了一套关于宇宙中最稀疏区域（宇宙空洞）相对于宇宙墙的AGN活动比例的约束。我们发现，在高和中光度的空洞星系中，中IR变化-AGN比例明显大于其墙类星系。我们还表明，中IR变化识别出一个相当大且独特的AGN群体，其中大部分通过传统的AGN选择方法（如单历元中IR颜色选择）未能被检测到。这些新恢复的AGN的比例在空洞中的星系中更高，这再次表明宇宙中最稀疏的大尺度结构中AGN活动更为频繁。 显示英文摘要

摘要： Observations and theoretical simulations suggest that the large scale environment plays a significant role in how galaxies form and evolve and, in particular, whether and when galaxies host an actively accreting supermassive black hole in their center (i.e., an Active Galactic Nucleus, or AGN). One signature of AGN activity is luminosity variability, which appears in the mid-infrared (mid-IR) when circumnuclear dust reprocesses UV and optical photons from the AGN accretion disk. We present here a suite of constraints on the fraction of AGN activity in the most underdense regions of the universe (cosmic voids) relative to the rest of the universe (cosmic walls) by using ~12 years of combined multi-epoch data from AllWISE and NEOWISE to quantify mid-IR variability. We find clear evidence for a larger mid-IR variability-AGN fraction among high and moderate-luminosity void galaxies compared to their wall counterparts. We also show that mid-IR variability identifies a rather large and unique population of AGNs, the majority of which have eluded detection using more traditional AGN-selection methods such as single-epoch mid-IR color selection. The fraction of these newly-recovered AGNs is larger among galaxies in voids, suggesting once again more prolific AGN activity in the most underdense large scale structures of the universe.