Origin of radio emission in radio-quiet AGN

Determine the physical mechanism responsible for the radio emission observed in radio-quiet active galactic nuclei, clarifying whether the emission arises from star formation-related synchrotron radiation, low-power jets, or AGN-driven winds/shocks, in order to establish the dominant process in this population.

Background

The paper highlights that the LOFAR Two-metre Sky Survey (LoTSS) is substantially deeper than FIRST, enabling new studies of radio-quiet AGN. However, most radio-quiet sources are unresolved in wide-area surveys, and often only total flux density is available. Even with spectral information, varying survey sensitivities hinder building complete samples, making radio morphology and brightness temperature measurements essential to distinguish physical origins.

Within radio-quiet AGN, several mechanisms can produce radio emission, including star formation, small-scale AGN jets, and shocks from AGN-driven winds. The authors note that coronal emission is thought to be negligible at MHz frequencies. Establishing which mechanism dominates is necessary for accurate interpretation of AGN–galaxy co-evolution and for constructing physically motivated radio luminosity functions.