Probing the Origin of Millimeter Emission in Radio-Quiet Changing-look AGNs

The origin of compact millimeter continuum emission in radio-quiet AGNs (RQ AGNs) remains unclear. We investigate the millimeter emission in the changing-look AGN NGC 1566 using ALMA Band-6 observations (~230 GHz) from 2014 to 2022. A strong correlation between the millimeter and X-ray flux suggests a shared origin. The spectral index (αmm) ranges from 0.1 to −0.3, consistent with a compact, optically thick source. The millimeter-to-X-ray flux ratio shows no clear dependence on the Eddington ratio but increases in the low-accretion state. Our findings favor synchrotron emission from the magnetized X-ray corona as the likely origin, highlighting millimeter emission as a potential tracer of AGN activity in RQ AGNs.