Actively accreting supermassive black holes generally have intrinsically powerful emission at X-ray energies. These X-rays are thought to be generated via scattering of ultra-violet and optical photons (from the accretion disk) off of relativistic particles in a corona above the accretion disk. This model broadly accounts for the time variability of the X-rays and the overall energetics observed, but this corona of relativistic particles has not had strong direct observational evidence. In “BASS XXXII: Studying the Nuclear Mm-wave Continuum Emission of AGNs with ALMA at Scales ≲ 100-200 pc” (Kawamuro+) we study ~230 GHz continuum emission from a number of X-ray AGN from the BAT AGN Spectroscopic Survey. We find a correlation between the small-scale (< 200 pc) millimeter continuum emission and the X-ray emission, suggesting that the millimeter emission may be self-absorbed synchrotron emission from the relativistic particles that are generating the X-ray emission.
The paper has been accepted for publication in The Astrophysical Journal and a preprint is available at the link above.