Active Galactic Nuclei: Accretion and Supermassive Black Holes

Dear Colleagues,

Active Galactic Nuclei (AGN) are among the most luminous and dynamic sources in the Universe, powered by accretion onto supermassive black holes (SMBHs) at the centers of galaxies. This Special Issue aims to explore the physical mechanisms governing AGN activity and their broad implications for black hole growth, galaxy evolution, and cosmology.

Topics of interest include the following: the physics of accretion disks, outflows, and supermassive black holes; the coupling between the central engine, broad-line region (BLR), and dusty surroundings; emission variability, with extreme cases of changing-look objects; main sequences of quasars, and implications for cosmology.

Particular emphasis will be placed on SMBH mass determinations via reverberation mapping, the radius–luminosity (R–L) relation, and scaling relations connecting AGN luminosity, black hole mass, and host galaxy characteristics. The emerging class of changing-look AGN provides unique insight into accretion state transitions and their characteristic timescales. Moreover, the quasar main sequence structured through the EV 1 parameter space offers a unifying framework linking accretion rate, emission-line behavior, and orientation effects, paving the way toward a deeper physical understanding of AGN diversity. Quasars also serve as powerful cosmological probes: their luminosity correlations, particularly in the super-Eddington regime, hold promise as alternative standard candles for constraining the expansion history of the Universe. Finally, studies of supermassive binary black holes and their gravitational wave signatures are highly encouraged.

This Special Issue invites observational, theoretical, and computational studies that advance our comprehensive understanding of AGN physics, variability, and their cosmological role.

Dr. Edi Bon
Dr. Nataša Bon
Guest Editors

Manuscript Submission Information

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• active galactic nuclei (AGN)
• accretion disks
• supermassive black holes (SMBH)
• broad-line region (BLR)
• dusty torus
• AGN unification (type 1 and type 2)
• changing-look AGN
• radius–luminosity relation
• black hole mass scaling
• quasar main sequence (eigenvector 1)
• supermassive binary black holes
• quasar cosmology