On the two main classes of Active Galactic Nuclei

Abstract

Active Galactic Nuclei (AGN) are traditionally divided empirically into two main classes: "radio-loud" and "radio-quiet" sources. These labels, which are more than fifty years old, are obsolete, misleading, and wrong. I argue that AGN should be classified based on a fundamentally physical rather than just an observational difference, namely the presence (or lack) of strong relativistic jets, and that we should use the terms "jetted" and "non-jetted" AGN instead.

Author's version of Nature Astronomy Comment. 5 pages, 1 figure. See https://www.nature.com/articles/s41550-017-0194

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