The origin of radio emission from radio-quiet active galactic nuclei

摘要

The central nuclei of galaxies, where supermassive black holes (SMBHs) are thought to reside, can experience phases of activitywhen they become active galactic nuclei (AGNs). An AGN can eject winds and jets and produce radiation across the entire electromagneticspectrum. The fraction of the bolometric emission in the radio spans a factor of approximately 105 across the differentclasses of AGNs. The weakest radio sources, radio-quiet (RQ) AGNs, are typically 1,000 times fainter than the radio-loud(RL) AGNs, and represent the majority of the AGN population. In RQ AGNs, the absence of luminous jets allows us to probe radioemission from a wide range of possible mechanisms: star formation, AGN-driven wind, free-free emission from photoionizedgas, low-power jets and the innermost accretion disk coronal activity. All these mechanisms can now be probed with unprecedentedprecision and spatial resolution, owing to the current and forthcoming generation of highly sensitive radio arrays.