AGN accretion

AGN accretion, the accretion of a supermassive black hole (SMBH) that constitutes a galaxy's active galactic nucleus (AGN), is of research interest, studied through observing active galaxies such as quasars, Seyfert galaxies, and radio galaxies. Observations show variations in characteristics between different AGNs as well as variations of an AGN over time. These are attributed to the material being accreted (the amount, type, and temperature), and to our viewing angle. Some terms for models of the accretion and associated accretion disks:

• alpha disk (aka thin disk, accreting material on the order of 10⁴-10⁷ K).
• advection dominated accretion flow (ADAF) (hotter material: can be MAD or SANE).
• standard and normal evolution (SANE).
• magnetically arrested disk (MAD).
• radiatively inefficient accretion flow (RIAF).
• slim disk (like alpha disk, but super-Eddington accretion).
• cold disk accretion (accretion via alpha disk).
• hot disk accretion (means ADAF).

Some of these models can also apply to circumstellar disks.