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[21.09] The Growth of Central Black Hole and the Ionization Instability of Quasar Disk

Ye Lu (National Astronomical Observatories, Chinese Academy of Sciences), K.S. Cheng (Dept. of Physics, U. Hong Kong), S.N. Zhang (document)

A possible accretion model associated with the ionization instability of quasar disks is proposed to address the growth of the central black hole harbored in the host galaxy. The evolution of quasars in cosmic time is assumed to change from a highly active state to a quiescent state triggered by the S-shaped ionization instability of the quasar accretion disk. For a given external mass transfer rate \dot{M}_ext supplied by the quasar host galaxy, ionization instability can modify accretion rate in the disk and separates the accretion flows of the disk into three different phases, like a S-shape. We suggest that the bright quasars observed today are those quasars with disks in the upper branch of S-shaped instability, and the faint or 'dormant' quasars are simply the system in the lower branch. The middle branch is the transition state which is unstable. We assume the quasar disk evolves according to the advection-dominated inflow-outflow solutions (ADIOS) configuration in the stable lower branch of S-shaped instability, and Eddington accretion rate is used to constrain the accretion rate in each phase. The mass ratio between black hole and its host galactic bulge is a nature consequence of ADIOS. Our model also demonstrates that a seed BH (~2\times 10⁶M_\odot) similar to those found in spiral galaxies today is needed to produce a BH with a final mass (~2\times 10⁸M_\odot).

This work was supported by the National Natural Science Foundation of China (NSFC 10273011) and the National 973 Project (NKBRSF G19990754).

Bulletin of the American Astronomical Society, 35#2
© 2003. The American Astronomical Soceity.