We review the results of the first multi-scale , hydrodynamical simulations of mergers between galaxies with central supermassive black holes ( SMBHs ) to investigate the formation of SMBH binaries in galactic nuclei .
We demonstrate that strong gas inflows due to tidal torques produce nuclear disks at the centers of merger remnants whose properties depend sensitively on the details of gas thermodynamics .
In numerical simulations with parsec-scale spatial resolution in the gas component and an effective equation of state appropriate for a starburst galaxy , we show that a SMBH binary forms very rapidly , less than a million years after the merger of the two galaxies , owing to the drag exerted by the surrounding gaseous nuclear disk .
Binary formation is significantly suppressed in the presence of a strong heating source such as radiative feedback by the accreting SMBHs .
We also present preliminary results of numerical simulations with ultra-high spatial resolution of 0.1 pc in the gas component .
These simulations resolve the internal structure of the resulting nuclear disk down to parsec scales and demonstrate the formation of a central massive object ( \sim 10 ^ { 8 } { M _ { \odot } } ) by efficient angular momentum transport due to the disk ’ s extended spiral arms .
This is the first time that a radial gas inflow is shown to extend to parsec scales as a result of the dynamics and hydrodynamics involved in a galaxy merger , and has important implications for the fueling of SMBHs .
Due to the rapid formation of the central clump , the density of the nuclear disk decreases significantly in its outer region , reducing dramatically the effect of dynamical friction and leading to the stalling of the two SMBHs at a separation of \sim 1 pc .
We discuss how the orbital decay of the black holes might continue in a more realistic model which incorporates star formation and the multi-phase nature of the ISM .