Millimeter emission from supermassive black hole coronae
Journal article, 2025
Context. Active galactic nuclei (AGNs) host accreting supermassive black holes (SMBHs). The accretion process can lead to the formation of a hot, X-ray emitting corona close to the SMBH that can accelerate relativistic electrons. Observations in the millimeter band can probe its synchrotron emission. Aims. We intend to provide a framework to derive physical information of SMBH coronae by modelling their spectral energy distribution (SED) from radio to far-infrared frequencies. We also explore the possibilities of deriving additional information from millimeter observations, such as the SMBH mass, and studying high-redshift lensed sources. Methods. We introduce a corona emission model based on a one-zone spherical region with a hybrid thermal and non-thermal plasma. We investigated the dependence of the corona SED on different parameters such as size, opacity, and magnetic field strength. Other galactic emission components from dust, ionised gas, and diffuse relativistic electrons were also included in the SED fitting scheme. We applied our code consistently to a sample of radio-quiet AGNs with strong indications of a coronal component in the millimeter. Results. The detected millimeter emission from SMBH coronae is consistent with a non-thermal relativistic particle population with an energy density that is -0.5-10% of that in the thermal plasma. This requires magnetic energy densities close to equipartition with the thermal gas and corona sizes of 60-250 gravitational radii. The model can also reproduce the observed correlation between millimeter emission and SMBH mass when we accounted for the uncertainties in the corona size. Conclusions. The millimeter band offers a unique window into the physics of SMBH coronae, enabling the study of highly dust-obscured sources and high-redshift lensed quasars. Gaining a deeper understanding of the relativistic particle population in SMBH coronae can provide key insights into their potential multiwavelength and neutrino emission.
Galaxies: nuclei
Radio continuum: galaxies
Submillimeter: galaxies
Radiation mechanisms: non-thermal
Author
Santiago Del Palacio
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Chentao Yang
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Susanne Aalto
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
C. Ricci
Diego Portales University
Beijing University of Technology
Boy Lankhaar
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Sabine König
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Julia Tjus
Ruhr-Universität Bochum
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
M. Magno
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
Texas A&M University
Krista L. Smith
Texas A&M University
Jun Yang
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Loreto Barcos-Munoz
University of Virginia
National Radio Astronomy Observatory
F. Combes
Paris Observatory
S. T. Linden
University of Arizona
C. Henkel
Xinjiang Astronomical Observatory
Max Planck Society
J. G. Mangum
National Radio Astronomy Observatory
S. Martin
Atacama Large Millimeter-submillimeter Array (ALMA)
European Southern Observatory Santiago
Gustav Olander
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
G. Privon
National Radio Astronomy Observatory
Clare Wethers
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Anne-Kathrin Baczko
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
R. J. Beswick
University of Manchester
I. García-Bernete
Centro de Astrobiologia (CAB)
S. G. Burillo
Spanish National Observatory (OAN)
E. Gonzalez-Alfonso
Spanish National Research Council (CSIC)
Mark Gorski
Northwestern University
M. Imanishi
National Astronomical Observatory of Japan
T. Izumi
National Astronomical Observatory of Japan
Sebastien Muller
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Y. Nishimura
University of Tokyo
M. Pereira-Santaella
Spanish National Research Council (CSIC)
P. van der Werf
Leiden University
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 701 A41Subject Categories (SSIF 2025)
Atom and Molecular Physics and Optics
Fusion, Plasma and Space Physics
Astronomy, Astrophysics, and Cosmology
DOI
10.1051/0004-6361/202554936