Origin of long-wavelength emission in radio-quiet quasars

Determine the physical origin of the long-wavelength (millimeter to radio) emission in radio-quiet quasars, distinguishing among proposed mechanisms such as coronal synchrotron emission, dust emission from the torus, star-formation-related processes, and low-power jets, to resolve the long-standing uncertainty about the dominant contributor.

Background

Understanding the source of long-wavelength emission in radio-quiet quasars is central to modeling active galactic nuclei (AGN) and their environments. Competing hypotheses include compact coronal synchrotron emission, thermal dust from the torus, star-formation-related free-free/synchrotron, and weak jets. Direct spatial resolution at the required sub-0.01 pc scales is beyond current facilities, motivating indirect probes such as microlensing.

This paper reports evidence favoring coronal emission in RXJ1131-1231 via microlensing-based size constraints and a mm–X-ray luminosity relation consistent with coronal expectations, but the broader population-level question remains open.